All Variables

The Hottest Day describes the warmest daytime temperature in the selected time period. In general, the hottest day of the year occurs during the summer months.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. However, when temperatures are very hot, people – especially the elderly – are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures.

Technical Description:

The highest maximum temperature (T_max) in the selected time period. Use the Variable menu option to view annual, monthly or seasonal values for this index.

Mean temperature describes the average temperature for the 24-hour day.

The average temperature is an environmental indicator with many applications in agriculture, engineering, health, energy management, recreation, and more.

Technical description:

The average of the daily maximum temperature (T_max) and the daily minimum temperature (T_min). Use the Variable menu option to view annual, monthly or seasonal values for this variable.

Minimum temperature describes the coldest temperature of the 24-hour day. Typically, but not always, the minimum temperature occurs at night and so this variable is commonly referred to as the nighttime low.

The average lowest temperature is an environmental indicator with many applications in agriculture, engineering, health, energy management, recreation, and more.

Technical description:

The daily minimum temperature (T_min). Use the Variable menu option to view annual, monthly or seasonal values for this variable.

Maximum temperature describes the warmest temperature of the 24-hour day. Typically, but not always, the maximum temperatures occur during the day and so this variable is commonly referred to as the daytime high.

The average highest temperature is an environmental indicator with many applications in agriculture, engineering, health, energy management, recreation, and more.

Technical description:

The daily maximum temperature (T_max). Use the Variable menu option to view annual, monthly or seasonal values for this variable.

Days with Max Humidex > 30 describes the number of days where the Humidex is greater than 30. This index gives an indication of the number of hot and humid days in the selected time period.

The Humidex was developed by the Meteorological Service of Canada to describe how hot and humid the weather feels to the average person. In Canada, it is recommended that outdoor activities be moderated when the Humidex exceeds 30, and that all unnecessary activities cease when it passes 40 (Environment and Climate Change Canada, 2019).

Technical description:

The number of days with a maximum Humidex (HX) over 30.

Use the Variable menu option to view annual, monthly or seasonal values for this index.

Read more

Days with Max Humidex > 35 describes the number of days where the Humidex is greater than 35. This index gives an indication of the number of hot and humid days in the selected time period.

The Humidex was developed by the Meteorological Service of Canada to describe how hot and humid the weather feels to the average person. In Canada, it is recommended that outdoor activities be moderated when the Humidex exceeds 30, and that all unnecessary activities cease when it passes 40 (Environment and Climate Change Canada, 2019).

Technical description:

The number of days with a maximum Humidex (HX) over 35.

Use the Variable menu option to view annual, monthly or seasonal values for this index.

Read more

Days with Max Humidex > 40 describes the number of days where the Humidex is greater than 40. This index gives an indication of the number of hot and humid days in the selected time period.

The Humidex was developed by the Meteorological Service of Canada to describe how hot and humid the weather feels to the average person. In Canada, it is recommended that outdoor activities be moderated when the Humidex exceeds 30, and that all unnecessary activities cease when it passes 40 (Environment and Climate Change Canada, 2019) Warm Season Weather Hazards.

Technical description:

The number of days with a maximum Humidex (HX) over 40.

Use the Variable menu option to view annual, monthly or seasonal values for this index.

Read more

Days with Tmin <-15°C describes the number of days where the lowest temperature of the day is colder than -15°C. This index gives an indication of the number of very cold days in the selected time period.

Cold weather is an important aspect of life in Canada, and many places in Canada are well adapted to very cold winters. Cold temperatures affect our health and safety, determine what plants and animals can live in the area, limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use.

Technical description:

The number of days with a minimum temperature (T_min) less than -15°C.

Use the Variable menu option to view annual, monthly or seasonal values for this index.

Days with Tmin <-25°C describes the number of days where the lowest temperature of the day is colder than -25°C. This index gives an indication of the number of extreme cold days in the selected time period.

Cold weather is an important aspect of life in Canada, and many places in Canada are well adapted to very cold winters. Cold temperatures affect our health and safety, determine what plants and animals can live in the area, limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use.

Technical description:

The number of days with a minimum temperature (T_min) less than -25°C. Use the Variable menu option to view annual, monthly or seasonal values for this index.

Days with Tmax > 25°C describes the number of days where the daytime high temperature is warmer than 25°C. This index gives an indication of number of summer days in the selected time period.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. However, when temperatures are very hot, people – especially the elderly – are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures.

Technical description:

The number of days with a maximum temperature (T_max) greater than 25°C. Use the Variable menu option to view annual, monthly or seasonal values for this index.

Days with Tmax > 27°C describes the number of days where the daytime high temperature is warmer than 27°C.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. However, when temperatures are very hot, people – especially the elderly – are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures.

Technical description:

The number of days with a maximum temperature (T_max) greater than 27°C. Use the Variable menu option to view annual, monthly or seasonal values for this index.

Days with Tmax > 29°C describes the number of days where the daytime high temperature is warmer than 29°C.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. However, when temperatures are very hot, people – especially the elderly – are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures.

Technical description:

The number of days with a maximum temperature (T_max) greater than 29°C. Use the Variable menu option to view annual, monthly or seasonal values for this index.

Days with Tmax > 30°C describes the number of days where the daytime high temperature is warmer than 30°C. This index gives an indication of number of hot days in the selected time period.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. However, when temperatures are very hot, people – especially the elderly – are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures.

Technical description:

The number of days with a maximum temperature (T_max) greater than 30°C. Use the Variable menu option to view annual, monthly or seasonal values for this index.

Days with Tmax > 32°C describes the number of days where the daytime high temperature is warmer than 32°C. This index gives an indication of number of very hot days in the selected time period.

High temperatures are important. They determine if plants and animals can thrive, they limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use. However, when temperatures are very hot, people – especially the elderly – are much more likely to suffer from heat exhaustion and heat stroke. Many outdoor activities become dangerous or impossible in very high temperatures.

Technical description:

The number of days with a maximum temperature (T_max) greater than 32°C. Use the Variable menu option to view annual, monthly or seasonal values for this index.

The Coldest Day describes the lowest nighttime temperature in the selected time period. In general, the coldest day of the year occurs during the winter months.

Cold weather is an important aspect of life in Canada, and many places in Canada are well adapted to very cold winters. Cold temperatures affect our health and safety, determine what plants and animals can live in the area, limit or enable outdoor activities, define how we design our buildings and vehicles, and shape our transportation and energy use.

Technical Description:

The lowest minimum temperature (T_min) in the selected time period. Use the Variable menu option to view monthly, seasonal and annual values for this index.

The Last Spring Frost marks the approximate beginning of the growing season for frost-sensitive crops and plants. When the lowest temperature of the day remains above 0°C for one consecutive day (before July 15^th) the date of the last spring frost is established.

Technical description:

The spring date after which there are no daily minimum temperatures during the growing season less than 0°C (T_min > 0°C). Because this variable is largely used to assess the beginning of the growing season in southern Canada, the latest possible date for a spring frost was set as July 15. Use the Variable menu option to view values for this index on the map.

The First Fall Frost marks the approximate end of the growing season for frost-sensitive crops and plants. When the lowest temperature of the day is colder than 0°C for one consecutive day (after July 15^th) the date of the first fall frost is established.

Technical description:

The first date in the fall (or late summer) on which the daily minimum temperature is less than 0°C (T_min < 0°C). Because this variable is largely used to assess the end of the growing season in southern Canada, the earliest possible date for a fall frost was set as July 15. Use the Variable menu option to view values for this index on the map.

The Frost Free Season is the approximate length of the growing season during which there are no freezing temperatures to kill or damage frost-sensitive plants. This index describes the number of days between the Last Spring Frost and the First Fall Frost.

Technical description:

The number of days between the date of the last spring frost and the date of the first fall frost, equivalent to the number of consecutive days during the ‘summer’ without any daily minimum temperatures below 0°C. Use the Variable menu option to view values for this index on the map.

Wet Days >=1mm describes the number of days where at least 1 mm of precipitation (rain and snow combined) falls in the selected time period. This index generally captures every day when there is measurable precipitation.

Adequate precipitation is crucial to water availability, agriculture, electricity generation and wildfire suppression.

Technical description:

The number of days with precipitation >= 1.0 mm. Use the Variable menu option to view the annual, monthly or seasonal values for this index.

Wet Days >=10mm describes the number of days where at least 10 mm of precipitation (rain and snow combined) falls in the selected time period.

Adequate precipitation is crucial to water availability, agriculture, electricity generation and wildfire suppression.

Technical description:

The number of days with precipitation >= 10 mm. Use the Variable menu option to view the annual, monthly or seasonal values for this index.

Wet Days >=20mm describes the number of days where at least 20 mm of precipitation (rain and snow combined) falls in the selected time period.

Adequate precipitation is crucial to water availability, agriculture, electricity generation and wildfire suppression.

Technical description:

The number of days with precipitation >= 20 mm. Use the Variable menu option to view the annual, monthly or seasonal values for this index.

Maximum 1-Day Total Precipitation describes the largest amount of precipitation (rain and snow combined) that falls within a single 24-hour day for the selected time period. This index is commonly referred to as the wettest day of the year.

Very high 1-day precipitation totals could be the result of intense, but short-lived precipitation events such as thunderstorms, or may be due to precipitation occurring steadily over the course of the day. Short duration, high intensity precipitation events may lead to flash flooding, particularly in urban areas where storm drains may be overwhelmed. Heavy snowfall events can cause damage to buildings and disrupt transportation services.

Technical description:

The largest precipitation total that falls in a single day in the selected time period. Use the Variable menu option to view annual, monthly or seasonal values for this index.

Total Precipitation describes the total amount of precipitation (rain and snow combined) that falls within the selected time period.

Precipitation significantly impacts water availability, agricultural practices, electricity generation and wildfire suppression.

Technical description:

The total amount of precipitation (mm) accumulated in the selected time period. Use the Variable menu option to view the annual, monthly or seasonal values for this variable.

Maximum 5-Day Precipitation describes the largest amount of precipitation (rain and snow combined) to fall over 5 consecutive days.

High precipitation totals can cause flooding in urban areas, damage to crops and roads, and erode top soil. Heavy snowfall events can cause damage to buildings and disrupt transportation services.

Technical Description:

The maximum total precipitation that falls over a consecutive 5-day period. Use the Variable menu option to view annual, monthly or seasonal values for this index.

The Maximum Number of Consecutive Dry Days describes the longest spell of days where less than 1mm of precipitation falls daily.

Periods of dry weather can impact agriculture, energy demands and water availability. Drought conditions may result when dry periods are long-lasting.

Technical Description:

The maximum number of consecutive days with precipitation below 1mm/day, within the selected time period. Use the Variables menu option to view annual, monthly or seasonal values for this index.

The Number of Periods with more than 5 Consecutive Dry Days describes the number of times when daily precipitation totals are less than 1mm a day for six or more days straight.

Periods of dry weather can impact agriculture, energy demands and water availability. Drought conditions may result when dry periods are long-lasting.

Technical Description:

The number of periods with more than 5 consecutive days with precipitation below 1mm/day, within the selected time period. Use the Variables menu option to view annual, monthly or seasonal values for this index.

The Standardised Precipitation Evapotranspiration Index (SPEI) is a drought index based on the difference between precipitation (P) and potential evapotranspiration (PET). Negative (positive) values indicate water deficit (surplus).

SPEI-3 describes the SPEI of the month selected from the drop-down menu and the previous 2 months. For example, to look at SPEI values for the summer (June, July and August), select August from the drop-down menu. The SPEI values displayed will be for August, July and June.

Drought can occur on a variety or timescales and impacts will depend on how widespread and how long-lived a drought is. Drought affects water availability, which is of particular importance to agriculture and hydro-electricity production.

Use the Variable menu option to view any 3-month period for this index. Remember to select the final month of your chosen 3-month period in the drop-down menu.

The Standardised Precipitation Evapotranspiration Index (SPEI) is a drought index based on the difference between precipitation (P) and potential evapotranspiration (PET). Negative (positive) values indicate water deficit (surplus).

SPEI-12 describes the SPEI of the month selected from the drop-down menu and the previous 11 months. For example, to look at annual SPEI values, select December from the drop-down menu. The SPEI values displayed will be for December and the previous 11 months (January to November).

Drought can occur on a variety or timescales and impacts will depend on how widespread and how long-lived a drought is. Drought affects water availability, which is of particular importance to agriculture and hydro-electricity production.

Use the Variable menu option to view any 12-month period for this index. Remember to select the final month of your chosen 12-month period in the drop-down menu.

Relative Sea Level Change is the change in ocean level relative to land. Whereas global sea-level change can be attributed to thermal expansion of water and meltwater from glaciers, ice caps, and ice sheets, relative sea-level change is the combination of the effects from global sea-level change and the vertical motion of the land.

Projected relative sea level change data is available for 2006 and for every decade from 2010-2100, relative to 1986-2005 conditions.

Read more

Frost Days describes the number of days where the coldest temperature of the day is lower than 0°C.

The number of frost days is an indicator of the length and severity of the winter season. A location with a large number of frost days is also likely to have a short growing season, since frost is harmful to many plants.

Technical description:

A day when the daily minimum temperature (T_min) is below 0°C. Use the Variable menu option to view the annual, monthly or seasonal values for this index.

This is a simple count of the days when the air temperature fluctuates between freezing and non-freezing temperatures on the same day. Freeze-thaw cycles can have major impacts on infrastructure. Water expands when it freezes, so the freezing, melting and re-freezing of water can, over time, cause significant damage to roads, sidewalks, and other outdoor structures.

 Technical description

A freeze-thaw cycle occurs when the daily maximum temperature (T_max) is higher than 0°C and the daily minimum temperature (T_min) is less than or equal to -1°C.

The Variable menu option provides annual values for this index. Visit the Analyze page to calculate this index at different temporal frequencies, or to use different threshold values.

Cooling degree days (CDDs) give an indication of the amount of space cooling, i.e., air conditioning, that may be required to maintain comfortable conditions in a building during warmer months. When the daily average temperature is hotter than the threshold temperature, CDDs are accumulated (see Degree Days Above). Threshold  values may vary, but 18°C is commonly used in Canada.   Larger CDD values indicate a greater need for air conditioning.

Technical description:

The number of degree days accumulated above 18°C in the selected time period. Use the Variable menu option to view the annual, monthly or seasonal values for this index. Visit the Analyze page to calculate degree days using different threshold temperatures.

Tropical Nights (Days with Tmin >18°C) describes the number of days where the nighttime low temperature is warmer than 18°C. 

Hot summer days and heat waves become particularly stressful if overnight temperatures do not provide cooling relief. Tropical nights make it more difficult for the body to cool down and recover from hot days.

Elderly people, the homeless, and those who live in houses or apartments without air conditioning are especially vulnerable during these heat events, particularly if they last for more than a few days.

Technical description:

A Tropical Night occurs when the daily minimum temperature (T_min) is greater than 18°C. Use the Variable menu option to view the annual, monthly or seasonal values for this index. Visit the Analyze page to calculate Tropical Nights using different minimum temperature thresholds.

Tropical Nights (Days with Tmin >20°C) describes the number of days where the nighttime low temperature is warmer than 20°C. 

Hot summer days and heat waves become particularly stressful if overnight temperatures do not provide cooling relief. Tropical nights make it more difficult for the body to cool down and recover from hot days.

Elderly people, the homeless, and those who live in houses or apartments without air conditioning are especially vulnerable during these heat events, particularly if they last for more than a few days.

Technical description:

A Tropical Night occurs when the daily minimum temperature (T_min) is greater than 20°C. Use the Variable menu option to view the annual, monthly or seasonal values for this index. Visit the Analyze page to calculate Tropical Nights using different minimum temperature thresholds.

Tropical Nights (Days with Tmin >22°C) describes the number of days where the nighttime low temperature is warmer than 22°C.  Hot summer days and heat waves become particularly stressful if overnight temperatures do not provide cooling relief. Tropical nights make it more difficult for the body to cool down and recover from hot days.

Elderly people, the homeless, and those who live in houses or apartments without air conditioning are especially vulnerable during these heat events, particularly if they last for more than a few days.

Technical description:

A Tropical Night occurs when the daily minimum temperature (T_min) is greater than 22°C. Use the Variable menu option to view the annual, monthly or seasonal values for this index. Visit the Analyze page to calculate Tropical Nights using different minimum temperature thresholds.

Growing degree days (GDD) are a measure of whether climate conditions are warm enough to support plant and insect growth. When the daily average temperature is warmer than the threshold temperature, growing degree days are accumulated (see Degree Days Above). For forage crops and canola, a threshold temperature of 5°C is generally used.

Technical description:

The number of degree days accumulated above a threshold temperature of 5°C in the selected time period. Use the Variable menu option to view the annual, monthly or seasonal values for this index. Visit the Analyze page to calculate degree days using different threshold temperatures.

Cumulative degree days above 0°C can be used to determine when climate conditions are warm enough to support the growth of certain plants and pests. When the daily average temperature is warmer than 0°C, degree days are accumulated (see Degree Days Above).

This index can be used to determine the range of some insects and other pests. For example, the black-legged tick, which carries Lyme disease, requires the accumulation of at least 2800 degree days above 0°C for its survival. Warmer conditions can speed the development rate of these species and lead to an extension of their geographical range.

Technical description:

The number of degree days accumulated above 0°C in the selected time period. Use the Variable menu option to view the annual, monthly or seasonal values for this index. Visit the Analyze page to calculate degree days using different threshold temperatures.

Heating degree days (HDDs) give an indication of the amount of space heating (e.g., from a gas boiler/furnace, baseboard electric heating or fireplace) that may be required to maintain comfortable conditions inside a building during cooler months. When the daily average temperature is colder than the threshold temperature, HDDs are accumulated (see Degree Days Below). Threshold values may vary, but 17°C or 18°C are commonly used in Canada. Larger HDD values indicate a greater need for space heating.

Technical description:

The number of degree days accumulated below 18°C in the selected time period. Use the Variable menu option to view the annual, monthly or seasonal values for this index. Visit the Analyze page to calculate degree days using different threshold temperatures.

Climate Zones for buildings are determined based on the unique climatic conditions of a particular region. The National Energy Code of Canada for Buildings (NECB) uses Heating Degree Days to define Climate Zones. In this case, Heating Degree Days (HDDs) are calculated using a threshold of 18°C. This metric indicates the potential heating required to maintain comfortable conditions inside a building.

Because the climate is changing, relying on historical data is no longer adequate and information about future climate is also required to design future-ready buildings.

Technical Description:

The NECB Climate Zones are classified based on the number of HDDs. The thresholds are shown in the table below.  Additional guidance about Climate Zones for buildings can be found on the Learning Zone.

NECB’s Building Climate Zone Classifications for Canada.

Ice Days describe the number of days where the warmest temperature of the day is not above 0°C.

In other words, this index indicates the number of days when temperatures have remained below freezing for the entire 24-hour period. This index is an indicator of the length and severity of the winter season.

Technical description:

A day when the daily maximum temperature (T_max) is less than 0°C. Use the Variable menu option to view the annual, monthly or seasonal values for this index.

Version 3.30 (2022-10-31) – this data is updated annually.

Intensity Duration Frequency (IDF) curves relate short-duration rainfall intensity with its frequency of occurrence and are often used for flood forecasting and urban drainage design.

Intense precipitation events can deliver large amounts of rain over short periods of time. This rain, as well as related flooding, can overwhelm storm drains, flood basements, wash out bridges and roads, and trigger landslides. To reduce the risk of these impacts, engineers, hydrologists, planners and decision makers need accurate information about extreme rainfall events. IDF curves are one important source of this information.

Climate change is expected to increase extreme rainfall in Canada. Because of this, IDF curves based on historical observations alone are inappropriate for long-term decision-making. To account for climate change impacts to extreme rainfall and IDF curves, Environment and Climate Change Canada recommends use of a scaling methodology. ClimateData.ca provides historical and climate change-scaled IDF data for all ECCC IDF stations in Canada.

Additional guidance about integrating climate change into IDF curves can be found on the Learning Zone. For further technical information on how IDF Curves are produced, please refer to Environment and Climate Change Canada’s Engineering Climate Datasets page or contact the Engineering Climate Services Unit at ec.scg-ecs.ec@canada.ca.

Climate Normals describe the average climate conditions of a particular location over a 30-year period.

At the end of each decade, Environment and Climate Change Canada calculates a new set of climate normals using observations from that decade. All member countries of the World Meteorological Organisation calculate climate normals. As they describe the most recent average climate conditions for a location, they are often used to put extreme events into context.

The climate normals offered here are based on Canadian climate stations with at least 15 years of data available during the current 30-year normal period.

The Future Building Design Value Summaries are location-based summaries of the building design values developed by  Environment and Climate Change Canada as part of the Climate-Resilient Buildings and Core Public Infrastructure (CRBCPI) project.

The values are obtained from the Pacific Climate Impacts Consortium (PCIC)’s Design Value Explorer and are summarized into a table alongside relevant supporting guidance and information for every location in the National Building Code of Canada (NBCC, 2015).

Historical values are from the NBCC 2015, Table C-2* while the future values are derived from regional climate model simulations (CanESM2-CanRCM4) and are presented for two levels of global warming 1.5°C and 3°C above the 1986-2016 baseline period.

These summaries are tailored to users who would consult the NBCC as part of their work, for climate-related design and planning needs.

Read more