Hailstorm Preparation
What is a hailstorm?
Hail is produced by strong thunderstorms. Hailstorms occur because precipitation takes the form of ice pellets and hard snow. Hail can be smaller than a pea or as large as a softball, and can be very destructive to plants and crops.
Hail is caused by the transformation of water droplets to ice when there is a temperature below 0°C and a catalyst in the form of freezing nuclei. Continued deposits of supercooled water cause the ice crystals to grow into hailstones.
The first sign that hail may be arriving is a growing whitening among the shafts of rain. Soon a rattling sound is heard, as hailstones strike roofs and pavements. The ground whitens, becoming slippery as hailstones cover grass and roadways.
May through September is the period of maximum hail occurrence in Alberta.
Why are hailstorms a problem in Alberta?
The high plains immediately east of the Rocky Mountains experience the most frequent hailstorms in North America, and have been referred to as “Hail Alley.” This area extends from northern Alberta into Montana and continues southeast to include eastern parts of Wyoming, Colorado, and New Mexico. The area also covers most of South Dakota, Nebraska, Kansas, Oklahoma, and west Texas.
Alberta suffered some of the worst natural disasters in Canada, and hailstorms played a role. Prior to the 1998 Ice Storm in Quebec, the 1991 Calgary hailstorm was Canada's most expensive natural disaster, with insured losses of over $342 million.
Devastating hailstorms in Canada have included:
- Hailstorm strikes Calgary - September 7, 1991. A storm lasting 30 minutes dropped 10-cm diameter hail in Calgary subdivisions, splitting trees, breaking windows and siding, and crushing birds. Homeowners filed a record 116,000 insurance claims, with property damage losses exceeding $342 million - the most destructive hailstorm ever and the second costliest storm in Canada.
- Hailstorm pounds Calgary and Winnipeg - July 24, 1996. Orange-sized hailstones racked up close to $300 million in property losses. Hail clogged storm sewers, causing extensive flooding in both cities. In Winnipeg, at least a third of the cars damaged had to be written off.
How do I prepare for a hailstorm?
- You should always have a battery-operated radio handy to listen to updates on the hailstorm activity in you area.
- Stay indoors no matter what personal property is outside.
- If the hailstorm has not hit, you should try to put your car in a garage to protect it from damage.
- If you are in your car, you should pull over to the side of the road and try to get underneath an overpass to shield your car from the hail.
Damage due to hailstorms
Hail can shatter windows, leave pockmarks in siding and ultimately destroy roof coverings.