Two galleries of reader hailstorm photos: here and here.

A ferocious storm that hammered parts of Calgary with hail stones larger than golf balls late Sunday, causing millions of dollars worth of damage, could have been much worse if cloud-seeding planes hadn’t attempted to calm it down.

“The storm was a monster,” said Terry Krauss, project director of the Alberta Severe Weather Management Society, which contracts American-based company Weather Modification Inc. to seed severe weather clouds in Alberta’s skies. The society is funded by a group of insurance companies with a goal of reducing hail damage claims.

Before the storm hit, Krauss said, the company sent all four of its cloud-seeding aircraft into the thick and swirling black clouds. The planes flew for more than 12 hours, shooting silver iodide, a chemical agent that helps limit the size of hail stones, at the top and base of the clouds, until midnight.

But despite the heavy seeding, golf-ball-sized hail stones pelted parts of Calgary late Sunday night, causing widespread damage to cars and homes.

“This one was a beast. It took everything we threw at it and still was able to wreak some havoc,” said Krauss. “I believe if we hadn’t seeded, it would have even been worse.”

Northeast Calgary was worst hit by the storm, where the hail was between five and six centimetres, said Environment Canada meteorologist John Paul Craig. Other parts of the city saw toonie-sized hail from a second storm system, said Craig.

Craig said Sunday’s storm was worse than Calgary’s last major hailstorm, which saw four-centimetre hail stones, in July 2010.

“These hail stones were just a little bit bigger,” he said.

At Royal Oak Audi in the city’s northwest, broken glass from smashed windows littered the lot Monday morning. Of the 85 new and used cars on the lot, general manager Murray Dorren said not a single car was spared from the storm.

“It’s devastating — that’s probably the best word I can come up with,” he said. “It’s unbelievable that Mother Nature can do this much damage in a very short time. I think it probably took a matter of 10 minutes and there’s millions of dollars worth of damage.

Dorren estimated the damage at about $2 million. Across the lot, the dinged-up vehicles looked like dimpled golf balls from the repetitive pounding of the sizable stones. Some windows and sunroofs were shattered, while others were pierced by the heavy hail.

“They look like bullet holes right through the windscreen,” salesman Nick Berkland said of the damage.

Insurance companies and brokers were inundated with calls all day as customers tried to file claims on their wrecked cars and homes.

Ron Biggs, claims director for Intact Insurance, said it’s too early to tell how many claims the hail event will spurn, although he said they received about two to three times their normal call volume on Monday.

Biggs said the level of damage so far appears to be similar to the July 2010 hailstorm, when Intact received about 12,000 hail damage claims.