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Table 25. Alerting parameters Environment Canada uses for issuing a Weather Advisory and/or Warning; Alert type Location Threshold criteria; Advisory: National, except Nunavik* A generic weather advisory. One example might be on days when funnel clouds are expected, but a Tornado alert would not be appropriate. Warning: National, except Nunavik*
This is the same as clicking on a province or territory on the National alert map. Selecting a region name will take the user to the top of the region alert page. Selecting the event name will take the user to the details for that event in that region’s alert page. Table 1. This is an example summary table of public weather alerts across Canada.
- On this page
- Alerts
- Current conditions
- Past temperatures, normals, averages and extremes
- Forecast
- Precipitation
- Wind
- Health related weather information
- Lightning
- Radar
•Alerts
•Current conditions
•Past temperatures, normals, averages and extremes
•Forecast
•Precipitation
•Wind
The difference between a warning, a watch, a special statement, and an advisory
When severe weather threatens, Environment and Climate Change Canada, the authoritative source of Weather Alerts 24/7, is here for you, issuing special alerts that notify those in affected areas so that they can take steps to protect themselves and their property from harm.
The type of alert used depends on the severity and timing of the event:
•Special Weather Statements are the least urgent type of alert and are issued to let people know that conditions are unusual and could cause concern.
•Advisories are issued for specific weather events (like blowing snow, fog, freezing drizzle and frost) that are less severe, but could still significantly impact Canadians.
•Watches alert you about weather conditions that are favorable for a storm or severe weather, which could cause safety concerns.
Why current temperature and/or weather at my home is different from the Environment and Climate Change Canada current conditions
•The current temperature for a region is taken at a local weather station.
•You can experience a significant temperature difference within just a few kilometers. Large differences in temperature are common especially in the early morning.
•A difference in elevation may result in a different temperature reading. Cold air tends to go to lower ground.
•Large bodies of water affects the air temperature along coastal sections. Usually, it can influence the temperature within 3 to 7 kilometers from the shore. The temperature may also vary depending on wind direction and speed, the water temperature and the cloud cover.
•The make and model of a sensor, its accuracy, and its exposure to the environment can also influence the measurement of local weather.
The difference in the temperature displayed in the ‘Past 24 hours’ and in the ‘Yesterday's data’
The ‘Past 24 hours’ temperatures are reported once every hour by the weather stations. As the temperature is monitored on a continuous basis, we notice that the daily maximum and minimum temperatures rarely happen exactly on the hour. So, the maximum and minimum temperatures in ’Yesterday’s data’ are usually different than the highest and lowest hourly temperatures.
The difference in the temperature displayed in the ‘Normals’ and the average in ‘Averages and extremes’
Climate Normals are calculated for 30-year periods. The Normals that we are using today are calculated from data for the period 1981-2010. They get updated every decade.
The temperatures in the ‘Normals’ section are regional normals, for which the average temperatures for a larger region are calculated on the same 30-year average. The regional normals are based on temperatures from several locations instead of just one. They will usually differ by one to three degrees compared with the average temperatures listed for an individual location in the ‘Averages and extremes’ section.
For more information about Normals, visit Canadian Climate Normals.
The different weather elements (snow, rain, wind, etc.) and when they are included in the forecast
Public weather program
To learn more about weather elements and when they are included in the forecast, visit Guide to public weather forecasts: weather elements.
Marine weather program
To learn more about what is included in the marine forecasts, visit: Guide to marine weather forecasts – What information is included in the Marine Forecast?
How weather forecasts are made and how often they are updated
The difference between shower, drizzle and flurry
When we mention rain in the forecast, it is associated with a large precipitation band. This is the case ahead of a warm front for example. It can last several hours or for a full day. The rain can be intermittent, meaning it can stop for short periods.
Showers are normally shorter in length lasting a few minutes to several hours with breaks in between. Showers are also convective, associated with clouds of vertical development. This is the case with cold fronts or showers or thunderstorms caused by daytime heating on a summer afternoon. Showers can occur when there is a disorganized area of precipitation over a region.
Drizzle is a water droplet that is bigger than the water droplet of fog but smaller than the water droplet of rain. Drizzle appears to float in the air but does eventually fall to the ground.
Flurries are precipitation in the form of snow from a convective cumulus-type cloud. They are characterized by the suddenness with which they start and stop, by their rapid changes in intensity, and usually by rapid changes in the appearance of the sky.
To learn more about weather and meteorological terms, visit: Weather and meteorology glossary.
When to include wind speed and direction in the forecast
Public weather program
Included in the forecast for Day 1 & 2? - Yes, if it meets the criteria.
Included in the forecast for Day 3 to 7? - Yes, if it meets the criteria.
Days one and two
The wind speed and direction are included in the forecasts when the wind speed is expected to be 20 km/h or more. Note that wind is included in the day 1 and day 2 forecasts only.
Humidex
The humidex and how is it measured The humidex is a Canadian innovation that was first used in 1965. It describes how hot, humid weather feels to the average person. The humidex combines the temperature and humidity into one number to reflect the perceived temperature. Because it takes into account the two most important factors that affect summer comfort, it can be a better measure of how stifling the air feels than either temperature or humidity alone. Range of humidex: degree of comfort 20 to 29: Little discomfort 30 to 39: Some discomfort 40 to 45: Great discomfort; avoid exertion Above 45: Dangerous; heat stroke possible An extremely high humidex reading is any reading over 40. In such conditions, you should reduce all unnecessary physical activity. If the reading is in the mid to high 30s, then you should tone down or modify certain types of outdoor exercise, depending on the individual age and health, physical shape, the type of clothes worn and other weather conditions. To learn more, visit: Warm season weather hazards: Heat and humidity.
Air quality and the Air Quality Health Index (AQHI)
More about the Air Quality Health Index (AQHI) The Air Quality Health Index (AQHI) is a scale designed to help you understand what the quality of the air around you means to your health. It is a tool developed by health and environmental professionals to communicate the health risk posed by air pollution. It is designed to help you make decisions to protect your health and the environment by: Limiting short-term exposure to air pollution Adjusting your activity during episodes of increased air pollution and encouraging physical activity on days when the index is lower Reducing your personal contribution to air pollution The index provides specific advice for people who are especially vulnerable to the effects of air pollution as well as the general public. The AQHI is a scale that lists a number from 1 to 10+ to indicate the level of health risk associated with air quality: 1-3 = ‘Low’ health risk 4-6 = ‘Moderate’ health risk 7-10 = ‘High’ health risk Above 10 = ‘Very high’ health risk To learn more, visit: About the Air Quality Health Index. How the Air Quality Health Index (AQHI) is calculated The Air Quality Health Index (AQHI) is designed as a guide to the relative risk presented by common air pollutants which are known to harm human health. Three specific pollutants have been chosen as indicators of the overall mixture: Nitrogen Dioxide (NO2), is released by motor vehicle emissions and power plants that rely on fossil fuels. It contributes to the formation of the other two pollutants. Nitrogen dioxide is often elevated in the vicinity of high traffic roadways and other local sources. Ground-level Ozone (O3), is formed by photo-chemical reactions in the atmosphere. It can be a major component of smog during the summer, especially during hot sunny weather, but is generally low in the wintertime. Ozone can be transported long distances within a polluted air mass and can be responsible for large regional air pollution episodes. Fine Particulate Matter (PM2.5), is a mixture of tiny airborne particles that can be inhaled deep into the lungs. These particles can either be emitted directly by vehicles, industrial facilities or natural sources like forest fires, or formed indirectly as a result of chemical reactions among other pollutants. Particulate matter can reflect both local air pollution sources or widespread air pollution episodes. All three can have serious, combined effects on human health (from illness to hospitalization to premature death), even as a result of short-term exposure. Significantly, all of these pollutants appear to threaten human health, even at low levels of exposure, especially among those with pre-existing health problems. In the development of the AQHI, a formula that combined these three pollutants was found to be the best indicators of the health risk of the combined impact of the mix of pollutants in the air. To learn more, visit: Air quality: frequently asked questions.
More about lightning and lightning safety
To learn more, visit: Lightning.
Learning how to use the radar
To learn more on the meaning of echoes and its intensity in the precipitation (rain, snow, etc…), and read and use the image as displaying system visit: About Canadian weather radar.
For historical single and composite radar images, visit: Canadian Historical Weather Radar.
Why some areas, particularly British Columbia, always seem to have precipitation
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- Nathan Howes
2024-10-09. Environment Canada's weather web site provides official weather warnings, current conditions, forecasts, and weather models, for public and marine areas in Canada. Canadian weather RADAR, tropical storm tracking, lightning activity, UV index, and AQHI index values also available.
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