Severe thunderstorms with golf-ball-sized hail set to strike Calgary today
Environment and Climate Change Canada has issued a high-risk thunderstorm alert for Calgary and surrounding areas, with wind gusts up to 130 km/h and rainfall up to 50 millimetres expected.
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Update — August 12, 2026: Environment Canada issued an orange warning for a dangerous thunderstorm moving southeast at 50 km/h over Claresholm, about 120 kilometres south of Calgary, with the warning covering areas including Barons, Coalhurst, Lethbridge County, Nobleford and Monarch. The agency warns that damaging wind gusts, golf ball- to tennis ball-sized hail and heavy rain are possible, with the potential for significant damage to buildings and trees and risk of serious injury.
Severe thunderstorms capable of producing very large hail are set to sweep through Calgary and surrounding areas today, Monday, August 10, according to Environment and Climate Change Canada.
A high-risk zone encompasses Calgary, Airdrie, Okotoks, Chestermere, Cochrane, Brooks, and Vulcan. Weather risks in that area include wind gusts of up to 130 kilometres an hour, thunderstorms that could produce hail up to five centimetres in size — roughly the equivalent of a golf ball — and rainfall totals of up to 50 millimetres.
Areas northwest of Edmonton, including Grande Prairie, Peace River, Whitecourt, and Edson, are under a moderate weather risk with potential for hail up to 2.5 centimetres, wind gusts up to 70 kilometres an hour, and rainfall up to 40 millimetres.
An additional minor weather risk zone covers most of the province, including Edmonton, Lloydminster, Banff, Jasper, Medicine Hat, and Lethbridge, with wind gusts up to 80 kilometres an hour, hail up to two centimetres in size, and rainfall up to 20 millimetres.
The thunderstorm risk continues into overnight hours, with an outlook for early Tuesday showing a minor risk for parts of the province. The strongest impacts will affect Lloydminster and Medicine Hat, with wind gusts up to 80 kilometres an hour, hail up to two centimetres, and 20 millimetres of rain.
Current weather watches and warnings are available on the ECCC website.
The facts
What size hail is expected in Calgary?
Hail up to five centimetres in size — roughly the equivalent of a golf ball — is expected in Calgary on Monday, August 10, 2026.
Which areas are under high-risk thunderstorm alerts?
Calgary, Airdrie, Okotoks, Chestermere, Cochrane, Brooks, and Vulcan are in the high-risk zone on Monday, August 10, 2026.
What wind speeds are forecast for Calgary?
Wind gusts up to 130 kilometres an hour are expected in Calgary on Monday, August 10, 2026.
How much rain could fall in the high-risk zone?
Rainfall totals of up to 50 millimetres are expected in the high-risk zone on Monday, August 10, 2026.
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