Brochures

Weather watches, warnings and advisories

• Severe thunderstorm watch
• Severe thunderstorm warning
• Tornado watch
• Tornado warning
• Freezing rain warning
• Heavy rain warning
• Frost warning
• Wind warning
• Marine wind warnings
• Dust storm advisory
• Blizzard warning
• Heavy snowfall warning
• Winter storm warning
• Windchill warning
• Cold wave advisory

For the safety of people and property, Environment Canada issues severe weather warnings and watches and advisories to the public via the media, weather outlets and Weatheradio Canada.

A WEATHER WATCH

alerts you that conditions are favourable for the development of severe weather. Watch the skies and listen for updated watches and possibly weather warnings.

A WEATHER WARNING

alerts you that severe weather is occurring or that hazardous weather is highly probable. Severe thunderstorm or tornado warnings may be issued less than one hour in advance. Other weather warnings may be issued six to twelve hours in advance.

A WEATHER ADVISORY

means actual or expected weather conditions may cause general inconvenience or concern, but do not pose a serious enough threat to warrant a weather warning. An advisory may also be used when conditions show signs of becoming favourable for severe weather when the situation is not definite enough or too far in the future to justify a warning.

This fact sheet lists some of the more common weather watches, warnings and advisories issued by Environment Canada. Note that criteria for warnings are established to meet local and regional needs and may vary slightly from region to region across Canada. Contact your nearest weather outlet to confirm criteria for your area.

Severe thunderstorm watch

Conditions are favourable for the development of severe thunderstorms with large hail, heavy rain, intense lightning or damaging winds within the areas and times specified in the watch. You should secure or put away loose objects such as outdoor furniture, put your car in the garage, bring livestock to shelter and listen carefully for an updated weather report.

Severe thunderstorm warning

A severe storm has developed, producing one or more of the following conditions: heavy rain, damaging winds, hail of at least 20 mm in diameter or intense lightning. Severe thunderstorms may also produce tornadoes. The storm's expected motion and developments will be given in the warning. If you are in the area specified, take shelter indoors.

Tornado watch

Conditions are favourable for the development of tornadoes within the areas and times specified in the watch. Be prepared to take shelter, preferably in the lower level of a sturdy building.

Tornado warning

One or more tornadoes are occurring in the area specified. The expected motion, development and duration will be given in the warning. If you are in the path of a tornado, take emergency precautions immediately. If you are near the area specified in the warning, be alert for the development of additional tornadoes or severe thunderstorms.

Freezing rain warning

Expect slippery walking and driving conditions, and possible damage to trees and overhead wires due to rain freezing on contact to form a coating of ice. Avoid travel.

Heavy rain warning

Issued when heavy or prolonged rainfall is sufficient to cause local/widespread flooding. Expect 50 mm of rain over 12 hours or less, or 80 mm of rain in less than 24 hours.

Frost warning

A frost warning is issued when air temperatures are expected to fall to near freezing or below during the growing season, approximately May 15 to October 15. Protect your plants!

Wind warning

Expect winds blowing steadily at 60 km/h or more, or winds gusting to 90 km/h or more, for at least one hour. Secure or put away loose objects such as outdoor furniture, put your car in the garage, and bring livestock to shelter.

Marine wind warnings

Small Craft Warning:

Issued if winds of 20 to 33 knots are forecast.

Gale Warning:

Issued if winds of 34 to 47 knots are forecast.

Storm Warning:

Issued if winds of 48 to 63 knots are forecast.

Hurricane Force Wind Warning:

Issued for winds of 64 knots or greater.

Dust storm advisory

Issued in the prairie provinces when blowing dust caused by high winds has reduced visibility to one kilometre or less. Under extreme conditions of widespread zero visibility, this bulletin may be issued as a warning. Dust can impair breathing for people and animals, and make travel hazardous.

Blizzard warning

Expect snow or blowing snow, with a severe windchill and visibility reduced to less than one kilometre, for four hours or more. Stock up on heating fuel and food. Stay indoors and wait out the storm.

Heavy snowfall warning

Expect a snowfall of 10 cm or more (15 cm or more in Ontario) in 12 hours or less. Travel could become hazardous.

Winter storm warning

Issued in Ontario when two or more winter conditions reach warning proportions (eg. wind and snow, or freezing rain followed by heavy snowfall). Be prepared to cancel travel plans and stay indoors.

Windchill warning

Expect very cold temperatures combining with wind to create outdoor conditions hazardous to human activity. Be prepared to stay indoors.

Cold wave advisory

Temperatures are expected to drop by 20 Celsius or more within 18 hours. Dress warmly and check the weather forecast before travelling or venturing outdoors.

This document is published by authority of the Minister of the Environment. Copyright Minister of Supply and Services Canada 1995. Catalogue number En57-24/24-1995E. ISSN 0715-0040. ISBN 0-662-22991-6.

The Green Lane^TM,
Environment Canada's World Wide Web Site.