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Special Weather Statements and Weather Warnings for the Atlantic Region
For the safety of people and property, Environment Canada issues severe weather warnings and special weather statements to the public via the media, weather outlets, the Internet, automated telephone answering devices and Weatheradio Canada.
A SPECIAL WEATHER STATEMENT 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. A Special Weather Statement may also be used when conditions show signs of becoming favorable for severe weather when the situation is not definite enough or too far in the future to justify a warning.
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 are generally issued 12 to 24 hours in advance.
This fact sheet lists some of the more common weather warnings and special weather statements issued for the public by Environment Canada's Atlantic Region Weather Centres. 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.
Public Winter Warnings Criteria
Blizzard Warning (Maritimes and Newfoundland) A blizzard warning is issued for the Maritimes and Newfoundland when all of the following conditions are met: winds greater than 40 km/h (21 knots); visibility less than one kilometre in snow, snow grains or blowing snow conditions; and temperatures less than or equal to -3°C. All of the above must persist for at least 4 hours.
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Blizzard Warning (Labrador) A blizzard warning is issued for Labrador when all of the following conditions are met: winds greater than 40 km/h (21 knots); visibility less than 1/2 mile (1 km) in snow, snow grains or blowing snow; and temperatures less than or equal to -7°C. All of the above must persist for at least 4 hours.
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Blowing Snow Warning Snow or Blowing Snow reducing visibility to less than 1 km (<5/8 mile) for the duration of 3 hours or more.
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Freezing Drizzle Warning A freezing drizzle warning is issued when freezing drizzle is expected for 7 hours or more in the Maritimes, (8 hours or more in Newfoundland and Labrador) or significant accumulation is expected. 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.
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Freezing Rain Warning A freezing rain warning is issued in situations where a hazard is likely to exist because of freezing precipitation. Freezing rain warnings are issued whenever 4 hours or more of continuous freezing rain are forecast. 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.
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Les Suêtes Wind Warning (Cape Breton) Les Suêtes wind warning uses the same criteria as a wind warning for the Maritimes. These winds occur over a specific area of the western Cape Breton Highlands during certain unique meteorological conditions. Les Suêtes is an Acadian phrase used to describe very strong southeast winds that occur in an area along the western coast of Cape Breton Island. Local fisherman report that the effects can extend 10 to 15 miles offshore. Because of the highly localized nature of these events this separate warning event is used. The warning covers a limited area of "Inverness County - Mabou and North." These can occur throughout the year, but are more frequent from the late fall through early spring.
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Rainfall Warning (Winter) During the winter months (December 15th to April 15th) when snow and frozen ground may limit proper drainage, a rainfall warning is issued when a rainfall of 25mm or more is expected over 12 hours or less. A warning may be issued for lesser rainfall amounts if drainage is expected to be particularly limited due to a recent heavy snowfall and frozen ground, resulting in a high potential for flooding.
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Snow squall Warning 15 cm of snow within 12 hours or under the snow squall visibility is near zero for 4 or more hours.
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Snowfall Warning A snowfall warning is issued when 15 centimetres or more of new snow are expected in a 24 hour period or less. In Newfoundland and Labrador, a snowfall warning is issued when 15 cm or more of new snow is expected in 12 hours or less.
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Storm Surge Warning A storm surge warning is issued when a storm surge and/or high waves may result in significant flooding in coastal areas.
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Wind Chill Warning (Labrador) Wind Chill values of -45, or colder, constitute a warning for Labrador.
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Wind Chill Warning (Maritimes and Newfoundland) A wind chill warning is issued when very cold temperatures combining with wind are expected which could create outdoor conditions hazardous to human activity. Wind Chill values of -35, or colder, constitute a warning in the Maritimes and Newfoundland.
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Wind Warning (Labrador and Newfoundland) An inland wind warning is issued for Newfoundland and Labrador if winds are expected to attain a steady speed of 75 km/h (40 knots), or to reach a speed of 100 km/h (54 knots) in gusts.
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Wind Warning (Maritimes) Though significant large scale wind events can occur throughout the year, the most active months are late fall, winter and early spring. An inland wind warning is issued for the Maritimes if winds are expected to attain a steady speed of 65 km/h (35 knots), or to reach a speed of 90 km/h (49 knots) in gusts.
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Winter Storm Warning A winter storm warning is issued either: when two or more winter warnings are expected including a snowfall warning or: a total water equivalent of 25 mm or more of precipitation is forecast within 12 hours. The individual types of precipitation must fall just short of warning criteria. For example, a forecast of 10 cm snow followed by 20 mm of rain.
Water equivalent refers to the amount of liquid water collected when frozen precipitation is completely melted. A 10 to 1 ratio is used to calculate the water equivalent of frozen precipitation. For example 10 cm of snow typically melts down to 10 mm of water. Thus 10 cm of snow has a water equivalent of 10 mm.
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Winter Storm Watch A winter storm watch is issued when conditions are favorable for the development of severe winter weather including: blizzard, snowfall, freezing rain, rainfall, winter storm. A winter storm watch is used when none of the winter warning thresholds are certain to be met, but significant weather is still expected to occur (For example, a forecast of 10 cm or more of snow changing through freezing rain to 10 mm or more of rain giving 20 mm or more of water equivalent).
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Wreckhouse Winds Wreckhouse is located between Cape Ray and St Andrew's in Southwestern Newfoundland. This area is, at times, subject to extremely violent southeast winds, which have been strong enough to blow rail cars off their tracks. |
Public Summer Warnings Criteria
Rainfall Warning A rainfall warning is issued, when necessary, from April 16th to December 14th when a rainfall of 50 mm or more in a 24 hour period is expected to occur. |
Severe Thunderstorm Watch A severe thunderstorm watch is issued when conditions are favourable for the development of severe thunderstorms. A severe thunderstorm watch can be issued up to six hours in advance of a severe thunderstorm developing.
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Severe Thunderstorm Warning A severe thunderstorm warning is issued for thunderstorms that meet one or more of the following conditions: wind gusts greater than 90 km/h; hail larger than 15mm in diameter (20 mm in Newfoundland and Labrador); rain - 25 mm in one hour OR 50 mm in three hours; tornado or tornadic waterspout.
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Tornado Warning Tornado warnings are issued up to 30 minutes before a tornado is forecast to move throughout the area.
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Storm Surge Warning A storm surge warning is issued when a storm surge and/or high waves may result in significant flooding in coastal areas.
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Frost Warning Frost warnings are issued when necessary from May 15 to October 15 (the growing season) for the Maritimes and from June 1st to September 30th for Newfoundland when temperatures are expected to fall to zero or below at grass level. A frost warning would normally be issued when forecast air temperature is +2°C or below. Frost warnings are not issued for Labrador but are mentioned in the forecast during the growing season.
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Humidex and Health Advisory During the summer months (June 1st to September 30th) whenever the forecast humidex is expected to reach or exceed 40 C, a humidex and health advisory is issued for the affected forecast regions.
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Marine Warnings Criteria
Small Craft Warning A warning of winds from 20 to 33 knots.
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Storm Force Winds A warning of winds from 48 to 63 knots.
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Gale Force Winds A warning of winds from 34 to 47 knots.
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Hurricane Force Winds A warning of winds of 64 knots or greater not necessarily associated with a storm of tropical origin.
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Freezing Spray Warning Moderate or heavy vessel icing expected.
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Ice Pressure Ice pressure is mentioned in the Marine Synopsis for ice pressure, closing leads, old ice (thicker than 100 cm) and intrusion in areas not normally prone to sea ice.
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Storm Surge Storm Surge is included in the Marine Synopsis when tide levels are expected to be 0.6 metres above the normal astronomical high tide.
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Sky Cover Terminology
For short term public forecast bulletin.
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Clear (night only) Used when the cloud amount is expected to cover 1 tenth of the sky or less on average for the period in question.
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Sunny Used when the cloud amount is expected to cover two tenths of the sky or less on average for the period in question.
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A few clouds (night only) Used when the cloud amount is expected to cover 2 to 3 tenths of the sky on average for the period in question.
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Sunny with cloudy periods Used when the cloud amount is expected to cover 3 to 4 tenths of the sky on average for the period in question.
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Cloudy periods (night only) Used when the cloud amount is expected to cover 4 to 6 tenths of the sky on average for the period in question.
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A mix of sun and cloud Used when the cloud amount is expected to cover 5 to 6 tenths of the sky on average for the period in question.
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Cloudy with sunny periods Used when the cloud amount is expected to cover 7 to 8 tenths of the sky on average for the period in question.
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Cloudy (night) Used when the cloud amount is expected to cover 7 to 10 tenths of the sky on average for the period in question.
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Cloudy (day) Used when the cloud amount is expected to cover 9 to 10 tenths of the sky on average for the period in question.
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Overcast Used when the cloud amount is expected to cover 10 tenths of the sky for the period in question.
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Increasing cloudiness Used when the cloud amount is expected to increase from 0 to 3 tenths to 7 to 10 tenths for the period in question.
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Clearing Used when the cloud amount is expected to decrease from 5 to 10 tenths to 0 to 3 tenths for the period in question.
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Sky Cover Terminology
For extended term public forecast bulletin
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Sunny Used when the cloud amount is expected to cover 0 to 3 tenths of the sky on average for the day in question.
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A mix of sun and cloud Used when the cloud amount is expected to cover 4 to 6 tenths of the sky on average for the day in question.
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Cloudy Used when the cloud amount is expected to cover 7 to 10 tenths of the sky on average for the day in question.
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Winds Forecast Terminology
The following gives the wind speeds equivalent to the descriptive terms used in the marine forecasts:
Marine Winds |
Light (less than 15 knots)
Moderate (15-19 knots)
Strong (20-33 knots)
Gale Force (34-47 knots)
Storm Force(48-63 knots)
Hurricane Force (64 knots or more)
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Temperature Forecast
Every regional forecast gives the range of temperature expected during the period. Temperatures can vary widely from point to point and are affected by wind direction and speed, elevation, and the presence of large bodies of open water. When wind speeds are high, temperatures are often uniform throughout a region. With calm conditions, a valley location may differ by as much as 10 degrees from temperatures near a hilltop. Winds off open water tend to keep temperatures lower in summer and higher in winter.
Chance of Precipitation (COP)
The Chance of Precipitation represents the likelihood of measurable precipitation occurring at any point in a region sometime during the forecast period. Essentially a 40% chance of rain implies that you have a 4 in 10 chance of getting wet in your location. COP allows the forecaster to indicate a degree of confidence through the use of a percentage. COP cannot be used to predict the location, time or how much precipitation will occur. A 60% chance of showers does not require amending if showers are occurring in a specific point in a region. Values are always included in the body of the forecast with precipitation. Only values 30, 40, 60 and 70 will be explicitly used.
0-20% - never mentioned
- No precipitation in the forecast.
30 & 40% events
- for convective type conditions; i.e. isolated, scattered variety
- for continuous type precipitation conditions; i.e. light, very light snow /rain variety
Only trace amount of precipitation is expected or alternatively reserved for conditions at the edge of continuous precipitation which will likely miss the forecast area.
50% - not mentioned
60 & 70% events
- for convective type conditions; i.e. showers/flurries
- for continuous type precipitation conditions; i.e. light rain/snow
More than trace amount of precipitation is expected, but not significant amounts (as determined regionally). Accumulations are not included in the forecast. Often used near the edge of continuous precipitation and there is a good chance some will be experienced in the area.
>70% - not mentioned explicitly
- for convective type conditions; i.e. showers / flurries / A few...
- for continuous type precipitation conditions; i.e. rain/snow/ Periods of...
Precipitation is expected (i.e. more than trace). Accumulations are mentioned in the forecast when expected to be regionally significant.
RISK - no COP mentioned
Risk can be used to augment a precipitation forecast. Risk must be accompanied with another form of precipitation. "Risk of" precipitation is reserved for high impact weather and will be used after the precipitation group (Thunderstorms, Hail, Freezing Rain and Freezing Drizzle).
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