Unprecedented damage caused by Aug. 20 hailstorm in Alberta and Saskatchewan: report

The Canadian Severe Storms Laboratory says the hailstorm that developed near Brooks, Alta., on Aug, 20, 2025, caused damaged home, properties and vegetation for 420 kilometres.

Researchers investigating two severe hailstorms in Alberta and Saskatchewan last week say one of the events tore a line of damage approximately 420 kilometres long across the landscape.

The Canadian Severe Storms Laboratory (CSSL) said three teams were dispatched to examine the impact of the storms that struck Alberta and Saskatchewan on Aug. 20, 2025.

The CSSL says the first storm began south of Diamond Valley at about 3 p.m. MT while the second, which was actually a cluster of supercell thunderstorms, initially formed near North Battleford, Sask., before 5:30 p.m. CT.

“In both cases, a combination of large hail and high winds played a direct role in the severity and extent of observed hail damage,” the CSSL said in a release.

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Using evidence collected by the teams, scientists determined the Brooks storm created a line of damage – or a “hail scar” – approximately 420 kilometres long, from Brant, Alta., to Beechy Provincial Pasture in Saskatchewan.

In that area, there were wrecked crops, broken windows, damaged roofs and moderate to severe siding damage.

The CSSL said the wind-driven hail damage was among the worst that the Northern Hail Project has ever documented.

That damage extended for more than 22 kilometres and affected an area six kilometres wide.

“Here, high volumes hail, with maximum estimated diameters of 40-50 millimetres, were driven by winds exceeding 120 km/h, likely reaching up to 165 km/h, over a period of 20 minutes or more. All buildings with plastic west-facing siding suffered 50 per cent to nearly 100 per cent siding removal, as well as severe damage to near-complete removal of underlying vapour barriers,” the CSSL said.

“Countless windows were blown out, with many structures with unsheltered west-facing windows suffering one or more complete breaches, resulting in wind, hail, rain and glass entering buildings and damaging contents. Roofs suffered a combination of wind and wind-driven hail damage. Asphalt shingles and underlays were heavily damaged by the hail and pulled up by the winds. Metal roofs in the area notably suffered severely from these combined impacts, displacing, denting, or removing roof cover panels and resulting in water intrusion.”

Natural features on the landscape didn’t fare any better, the CSSL said, with deciduous trees being stripped of foliage and windward-facing sides of coniferous trees being stripped of all foliage and branches.

Fields of crops such as grain and corn were levelled and grasslands were also impacted with root systems exposed and shrubs damaged.

“Hail volumes were such that the ground was covered to a depth of several centimetres, with hail drifts remaining along building perimeters over 48 hours after the event,” CSSL said.

The agency also said flocks of wild birds and poultry were killed by hail. Several large livestock also died, but it is unclear whether the animals died from hail or from being hit by branches and trees felled during the high winds.

“Within Brooks, very large (50-70 millimetre) hail was accompanied by lower wind speeds, but still resulted in widespread siding, window, roof and vehicle damage across the majority of the community. Severe hail damage to homes continued well to the northeast, most notably in the communities of Patricia, Alberta and Jenner, Alberta.”

Saskatoon storm

The CSSL also released details of a storm northeast of Saskatoon, which was “less severe” than the Brooks event, but still significant.

“A satellite-visible swath of vegetation/crop damage generated by the wind-driven hail is present from north of Fielding, eastwards to south of Cudworth, a distance of over 120 kilometres,” the CSSL said.

Reports of tennis ball to baseball-sized hail came in from the western portion of the storm’s track, which damaged vehicles and levelled canola fields.

Some of the worst affected areas of that storm included Hague, Sask., where large hailstones exceeding 50 millimetres in size were found.

Winds also reached about 155 km/h in that area, the group said.

The CSSL is continuing to collect and assess the data collected from both storms.