Public weather forecast bulletins

There are two types of public weather forecast bulletins: the regular forecast bulletin, and the extended forecast bulletin.

The regular public forecast bulletin provides a description of the most significant weather conditions expected within the next two days (refer to Table 1 for exact time periods).

The extended forecast bulletin provides a description of the anticipated weather conditions beyond the time period covered by the regular public forecast bulletin: days three to seven. This extended forecast (also referred to as the long range forecast) is more general than the regular forecast.

• Issuing time of forecasts
• Time period covered by forecasts
• Determination of forecast regions
• Forecast time period terminology
• What information is included in the forecast?
• Sample forecast
  • Sample regular forecast (text bulletin)
  • Sample extended forecast (text bulletin)
• Forecast Revision
• Hourly Forecasts

Issuing time of forecasts

Although there are some regional differences, the regular and extended public forecast bulletins are most commonly issued three times a day, at 5:00 a.m., 11:00 a.m., and 4:00 p.m. local time. Issue times of a few bulletins are different from the national standard due to time zone differences within a region.

Time period covered by forecasts

The following table indicates the time period that the forecast covers for each of the three above-mentioned forecast issue times.

Table 1. Time periods for the public forecast bulletin

Below, the same information can be seen along a timeline:

5:00 a.m. forecast issue

The timeline starts with the Today period, which covers the times of 5:00 a.m. to 6:00 p.m. It moves on to the Tonight period, which covers the times of 6:00 p.m. to 6:00 a.m. It then goes into the Tomorrow period, which covers the times of 6:00 a.m. to midnight. Lastly, the timeline includes the Days Three to Seven period, which covers the times of 6:00 am to 6:00 p.m.

11:00 a.m. forecast issue

The timeline starts with the Today period, which covers the times of 11:00 a.m. to 6:00 p.m. It moves on to the Tonight period, which covers the times of 6:00 p.m. to 6:00 a.m. It then goes into the Tomorrow period, which covers the times of 6:00 a.m. to midnight. Lastly, the timeline includes the Days Three to Seven period, which covers the times of 6:00 am to 6:00 p.m.

4:00 p.m. forecast issue:

The timeline starts with the Tonight period, which covers the times of 4:00 p.m. to 6:00 p.m. It moves on to the Tomorrow period, which covers the times of 6:00 a.m. to 6:00 p.m. It then goes into the Tomorrow night period, which covers the times of 6:00 p.m. to 6:00 a.m. Lastly, the timeline includes the “Days Three to Seven” period, which covers the times of 6:00 am to 6:00 p.m.

Determination of forecast regions

Forecast regions are closely aligned with cities, communities and municipal boundaries. Local factors such as terrain, climatology, land cover and population patterns were used to define these regions. The names of the forecast regions generally correspond with those of the most prominent communities or the geographic regions. All official place names can be found in the Canadian Geographical Names Database.

Forecast time period terminology

Table 2a. Terms for Day One and Day Two

Table 2b. Terms for Day Three (4 p.m. forecast only)

*Note: There are no time qualifiers for days four to seven. 

What information is included in the forecast?

Days One & Two

The regular public forecast bulletin will always contain the following standard weather elements: (see the Weather Elements and when they are included in the forecast, for further details)

• Sky condition / Precipitation (including type)
• Maximum temperature
• Minimum temperature

The following additional weather elements may also be included, provided certain criteria are met (see the Weather Elements and when they are included in the forecast for these criteria):

• Chance of Precipitation (COP)
• Precipitation amount
• Combinational events (e.g. blizzard)
• Wind
• Obstructions to Visibility(e.g.fog)
• Weather events (e.g. thunderstorm)
• Thermal indices (Wind chill, Humidex)
• Ultraviolet Index (UVI)

Days Three to Seven

The extended public forecast bulletin will always contain the following standard weather elements (see the Weather Elements and when they are included in the forecast, for further details).

• Sky condition / Precipitation  (including type)
• Minimum temperature
• Maximum temperature
• *Normals for the period

The following additional weather elements may also be included, provided certain criteria are met (see the Weather Elements and when they are included in the forecast for these criteria):

• Chance of precipitation (COP)
• Combinational events (e.g. blizzard)
• Wind
• Obstructions to visibility(e.g.fog)
• Weather events (e.g. thunderstorm)

*Note: The normal temperatures for this period are the climatic normal temperatures for the grouping of regions indicated in the forecast. It is the Day Five normal temperature that is displayed in the extended bulletin. The normal temperatures can change as the grouping of regions in the forecast is changed.

The climatic normal temperatures are derived from 30-year averages of daily highs and lows.

Sample forecast

SAMPLE forecast #1 from the Canada.ca/weather

1. Navigational toolbar that allows you to quickly link to other meteorological products and educational resources offered by Environment Canada; from radar and satellite images, marine information to fact sheets and Frequently Asked Questions.
   
2. The Forecast Quick Link lets you easily browse through each city to find your local weather forecast.
   
3. The watch/warning/advisory bannerwill warn you of all latest weather watches, warnings and advisories in effect for your region.  Clicking on the banner will take you directly to the full details of the message.
   
4. The Current Conditions box displays all available weather information for the location chosen, along with the time and date that the information is valid.
   
5. Forecast Iconsgive a visual description of what the forecast is for the next 5 days.  The icons will show the sky condition/precipitation,COP, high temperature and low temperature for each day.
   
6. The Forecast Text is the complete forecast and gives more information than the forecast icons.  In addition to the information given in the icons, the text is more descriptive and gives the wind speed and direction. 
   
7. The More Info tabs throughout the city page are drop down menus that will give you quick links to other useful information that pertains to the block that they are in.  The top tab will link you to the past 24 hour conditions, radar imagery and satellite imagery; the middle one will link you to the text forecasts, air quality and the UV index forecast; while the bottom tab will link you to record values and historical weather.
   
8. The Historical Data provides us with a quick summary of yesterday’s temperatures and precipitation, along with normal temperatures for the period, sunrise and sunset.

Sample regular forecast (text bulletin)

1. This text is called the “title block”. It indicates the forecast area, the date & the time for which the forecast is. It also indicates when the next forecast will be issued.
2. The forecast region name(s) is the full name of the region(s) or metropolitan area(s) for which the forecast is issued.
3. These are called “status statements”. If there is a watch, warning or an advisory in effect for a forecast region(s), then status statements are indicated.
4. The forecast text is broken into distinct periods (i.e. today, tonight, tomorrow) for ease of readability. See section 1.2 to learn more about the hours associated with the different time periods.

Sample extended forecast (text bulletin)

1. This text is called the “title block”. It indicates the forecast area, the date and the time for which the forecast is. It also indicates when the next forecast will be issued.
2. The forecast region name(s) is the full name of the region(s) or metropolitan area(s) for which the forecast is issued.
3. The extended forecast bulletin covers day 3 to day 7.

Forecast Revision

Forecasts are revised when the difference between the forecast and actual conditions are such that public security and safety are at risk and/or when inconvenience to the public is thought to be extensive. A revision to the regular public forecast bulletin is initiated when one or more of the following criteria have been satisfied:

• The non-occurrence of forecast precipitation or hazards (freezing rain, definite forecast of thunderstorms, etc.) and vice versa.
• A difference in precipitation type (snow as opposed to rain/freezing rain and vice versa).
• A significant change in the timing of forecast event(s).
• A marked change in temperature regime is expected but is not occurring and vice versa.
• When, to the opinion of the supervisor on duty, the latest forecast does not reflect what is actually occurring and what is expected to occur in the next few hours.

The extended forecast is rarely revised, however if it is revised, one or more of the same criteria above would have to be met to warrant the change(s).

Hourly Forecasts

Environment and Climate Change Canada provides a 24 Hour Forecast link in the upper right hand corner of the Forecast section. If you click on the link it will lead you to the weather forecast information for the next 24 hours. The hourly forecast information appears in a table and shows more detail than our text forecasts.

The table will be updated on an hourly basis, and will always provide 24 hours of information, starting with the next hour.

Sample - 24 Hour Forecast

Special Weather Statement In Effect

This table shows the weather forecast for the next 24 hours.
Date/Time (EDT)	Temp. (°C)	Weather Conditions	LOP†	Wind (km/h)	Humidex
21 July 2023
17:00	25	Cloudy	0	S 20	30
18:00	25	Cloudy	0	S 20	30
19:00	24	Cloudy	0	S 20	29
20:00	23	Cloudy	0	S 20	29
21:00	22	Chance of showers	30	S 20	28
22:00	21	Chance of showers	30	S 20	27
23:00	-21	Chance of showers	30	S 20	27
22 July 2023
00:00	20	Chance of showers	30	SE 20 gust 40	26
01:00	20	Chance of showers	30	SE 20 gust 40	26
02:00	19	Chance of showers	30	SE 20 gust 40	*
03:00	19	Chance of showers	30	SE 20 gust 40	*
04:00	19	Chance of showers	30	SE 20 gust 40	*
05:00	20	Chance of showers	30	SE 20 gust 40	27
06:00	20	Chance of showers	60	SE 20 gust 40	27
07:00	20	Chance of showers	60	SE 20 gust 40	27
08:00	20	Chance of showers	60	SE 20 gust 40	28
09:00	20	Chance of showers	60	SE 20 gust 40	28
10:00	20	Periods of rain. Risk of thundershowers	100	NW 30 gust 50	28
11:00	21	Periods of rain. Risk of thundershowers	100	NW 30 gust 50	29
12:00	21	Periods of rain. Risk of thundershowers	100	NW 40 gust 60	29
13:00	21	Periods of rain. Risk of thundershowers	100	NW 40 gust 60	29
14:00	21	Periods of rain. Risk of thundershowers	100	NW 40 gust 60	29
15:00	21	Periods of rain. Risk of thundershowers	100	NW 40 gust 60	29
16:00	21	Periods of rain. Risk of thundershowers	100	NW 40 gust 60	29

* Value not significant.

What is included in the 24 Hour Forecast?

The information displayed will consist of the following weather elements:

• Temperature: a value representing the temperature for the following hour.
• Weather conditions: an image and short summary text representing the most probable weather in the following hour.
• Likelihood of Precipitation (LOP): the chance of precipitation in the following hour.
• Wind: wind speed and direction for the following hour. If there are gusts in the forecast, this information will also be displayed. The letters VR indicate a variable wind direction during the hour.
• Wind chill: the wind chill for the following hour. If there are no wind chill values to display for the entire 24 hour period, this column will not appear. Further information on wind chill can be found at the following link: Learn more about Wind Chill.
• Humidex: the Humidex for the following hour. If there are no Humidex values to display for the entire 24 hour period, this column will not appear. Further information on Humidex can be found here: Learn more about Humidex.

Similar to the city pages, alert banners will display at the top of the page if an alert is in effect.