Hourly Weather

Temperature (°C)

The temperature of the air in degrees Celsius (C).

Dew Point Temperature (°C)

The dew point temperature in degrees C, a measure of the humidity of the air, is the temperature to which the air would have to be cooled to reach saturation with respect to liquid water. Saturation occurs when the air is holding the maximum water vapour possible at that temperature and atmospheric pressure. See also http://www.weatheroffice.gc.ca/mainmenu/faq_e.html

Relative Humidity (%)

Relative humidity in percent is the ratio of the quantity of water vapour the air contains compared to the maximum amount it can hold at that particular temperature.

Wind Speed (km/h)

The speed of motion of air in km/hr, usually observed at 10 m above the ground.

Wind Direction (10's Deg)

The direction (true or geographic, not magnetic) from which the wind blows. Expressed in ten's of degrees, 9 means 90 degrees true or an east wind, and 36 means 360 degrees true or a wind blowing from the geographic north pole. A value of zero (0) denotes a calm wind.

Visibility (km)

Visibility in kilometers (km) is the distance at which objects of suitable size can be seen and identified. Atmospheric visibility can be reduced by precipitation, fog, haze or other obstructions to visibility such as blowing snow or dust.

Station Pressure (kPa)

Atmospheric pressure in kiloPascal (kPa) is the atmospheric pressure (or force per unit area) exerted by the atmosphere as a consequence of the mass of air in a vertical column from the elevation of the observing station to the top of the atmosphere.

Occurrence of Weather and Obstructions to Vision

Observations of atmospheric phenomenon including the occurrence of weather and obstructions to vision have been taken at many hourly reporting stations. The current standard for these observations is the Manual of Surface Weather Observations, Chapter 3, Atmospheric Phenomena.

The phenomena that are reported are:

Tornado
Waterspout
Funnel Cloud
Thunderstorms
Heavy Thunderstorms
Rain*
Rain Showers*
Drizzle*
Freezing Rain*
Freezing Drizzle*
Snow*
Snow Grains*
Ice Crystals
Ice Pellets*
Ice Pellet Showers*
Snow Showers*
Snow Pellets*
Hail*
Fog
Ice Fog
Smoke
Haze
Blowing Snow
Blowing Sand
Blowing Dust
Dust
Freezing Fog

Precipitation types marked with an asterisk (*) are observed in three intensities: light, moderate and heavy. If the precipitation is listed in the WEATHER column without a modifier then the intensity is light. Otherwise it will appear with a modifier of moderate or heavy.

At some stations observations are made by automatic aviation weather reporting systems. The types of phenomena reported from these systems are not as numerous and are limited to:

Rain
Snow
Drizzle
Hail
Freezing Rain
Freezing Drizzle
Unknown Precipitation

Currently, the observation of Unknown Precipitation is not reported in the WEATHER column. The other precipitation types are reported.

When no weather or obstructions to visibility occur, sky conditions are provided reflecting the observation of total cloud amount. The following terms are used, based on the amount (in tenths) of cloud covering the dome of the sky:

Clear (0 tenths)
Mainly clear (1 to 4 tenths)
Mostly cloudy (5 to 9 tenths)
Cloudy (10 tenths)

These observations of cloud amounts are not available from aviation automatic weather stations.

Humidex

The humidex is an index (a computed value as opposed to something measured) devised to describe how hot or humid weather feels to the average person. The humidex combines the temperature and humidity into one number to reflect the perceived temperature. It takes into account these two important factors that affect summer comfort. It is therefore a better measure of how stifling the air feels than either temperature or humidity alone.

For more information regarding the relative humidity and the humidex, consult our fact sheet on humidity.

Wind Chill

Wind chill is the cooling effect of the wind in combination with low temperatures. When it is windy, we feel colder because our skin temperature is lower. This sensation of cold is what the wind chill index quantifies: as such, the index is not a real temperature and is expressed without units, even though it is calibrated according to the Celsius temperature scale.

You will find more details in our wind chill Web site.

Daily Weather

Maximum Temperature (°C)

The maximum temperature in degrees Celsius reached at the location for that day.

Minimum Temperature (°C)

The minimum temperature in degrees Celsius reached at the location for that day.

Maximum Relative Humidity (%)

The maximum value of all hourly relative humidity values for the day.

Minimum Relative Humidity (%)

The minimum value of all hourly relative humidity values for the day.

Total Rain (mm)

The total rainfall, or amount of all liquid precipitation such as rain, drizzle, freezing rain, and hail, observed during the day.

Total Snow (cm)

The total snowfall, or amount of frozen (solid) precipitation in cm such as snow and ice pellets, observed during the day.

Total Precipitation (mm)

The sum of the total rainfall and the water equivalent of the total snowfall observed during the day.

Snow on the Ground (cm)

The depth of snow in centimetres (cm) on the ground. Daily values displayed are measured during the early morning. Monthly values displayed are for the final day of the month.

Direction of Maximum Gust (10's Deg)

The direction of the maximum gust (true or geographic, not magnetic) from which the wind blows. Expressed in ten's of degrees (10's Deg), 9 means 90 degrees true or an east wind, and 36 means 360 degrees true or a wind blowing from the geographic north pole. This value is only reported if the maximum gust speed exceeds 29 km/hr.

Speed of Maximum Gust (km/h)

The speed in kilometres/hour (km/h) of the maximum wind gust during the day. The gust is the maximum or peak instantaneous or single reading from the anemometer (the instrument used to observe wind speed) during the day. The duration of a gust typically corresponds to an elapsed time of from 3 to 5 seconds.

Mean Temperature (°C)

The mean temperature in degrees Celsius (C) is defined as the average of the maximum and minimum temperature during the day.

Heating Degree Days

Heating degree-days for a given day are the number of Celsius degrees that the mean temperature is below 18°C. If the temperature is equal to or greater than 18°C, then the number will be zero. For example, a day with a mean temperature of 15.5°C has 2.5 heating degree-days; a day with a mean temperature of 20.5°C has zero degree-days. Heating degree-days are used primarily to estimate the heating requirements of buildings.

Cooling Degree Days

Cooling degree-days for a given day are the number of Celsius degrees that the mean temperature is above 18°C. If the temperature is equal to or less than 18°C, then the number will be zero. For example, a day with a mean temperature of 20.5°C has 2.5 cooling degree-days; a day with a mean temperature of 15.5°C has zero degree-days. Cooling degree-days are used primarily to estimate the air-conditioning requirements of buildings.

Monthly Weather

Snow on the Ground on the Last Day(cm)

The depth of snow in centimetres (cm) on the ground. Daily values displayed are measured during the early morning. Monthly values displayed are for the final day of the month.

Station Metadata

Latitude & Longitude

Latitude and longitude in degrees are usually recorded to the nearest second or to the nearest 0.003 of a degree. Negative values of longitude denote degrees west of the Greenwich meridian. All locations in Canada have negative values of longitude.

Elevation

The elevation in metres (m) refers to the elevation of the observing location above mean sea level.

Climate ID

The Climate ID is a unique identifier assigned by the Meteorological Service of Canada for each location having archived observations.

TC ID

The TC ID is the identifier assigned by Transport Canada to identify meteorological reports from airport observing sites transmitted in real time in aviation formats.

WMO ID

The WMO ID is an international identifier assigned by the Meteorological Service of Canada to standards of the World Meteorological Organization for stations that transmit observations in international meteorological formats in real time.