Ontario has been stuck in a pattern of intense heat followed almost immediately by severe thunderstorms. Record heat hit much of Ontario and Quebec on July 1, with a humidex of 46°C in Ottawa, and that same heat triggered thunderstorms that caused widespread flooding and storm damage the same day.

Just two weeks later, another heat wave peaked near 38°C in Toronto, fueling severe thunderstorms capable of producing destructive wind gusts, large hail and a few tornadoes.

Extreme heat causes a specific type of damage called a thermal stress crack. It happens when one part of a window gets much hotter than another and the glass can’t expand evenly, and that uneven expansion pulls the glass apart until it fractures, usually starting at the edge and running straight across the pane.

This is common right now because a heat wave doesn’t heat your whole window at once. A shaded corner stays cooler while the rest bakes in direct sun. Large, fixed windows on shaded or recessed walls face the highest risk, and older windows with standard glass are more vulnerable than newer tempered or heat-strengthened glass. If your AC is blasting cold air straight at a sun-baked window, you’re adding fuel to the fire.

Not every crack this summer came from a hailstone. Heat cracks and impact cracks look and behave differently, and knowing which one you have matters for repair.

That distinction isn’t just cosmetic. A heat crack usually means your existing glass reached its limit and needs replacing before it spreads further. A hail or wind-driven debris crack is a direct impact event, which matters a lot when it’s time to file an insurance claim.

Storm and hail damage is now one of the most expensive problems Canadian insurers deal with every single year.

Insured losses from severe weather in Canada exceeded $2.4 billion in 2025 alone, and total catastrophic weather claims hit $8.6 billion in 2024, with Ontario flooding alone accounting for $990 million of that.

Costs like these are a big reason home insurance premiums keep climbing across the province. Between 2016 and 2025, annual insured losses from catastrophic weather and wildfires in Canada totaled $37 billion, nearly tripling the $14 billion recorded the decade before. Every broken window this summer is part of that bigger, costlier trend.

Boarding up a broken window counts as protecting your home from further damage, and most policies expect (and cover) that step. Document the original damage first, then the temporary board-up, since insurers can’t verify what happened if the evidence gets cleaned up or repaired before they’ve inspected it.

Save your receipts. Don’t rush into a full permanent repair before your insurer has had a chance to see the damage themselves.

Standard home and business insurance policies cover damage caused by hail or wind, including damage from flying debris or water entering suddenly through a wind- or hail-caused opening.

Pre-existing damage, like a crack that was already there before the storm, generally isn’t covered.

Every policy is different, so it’s worth confirming your specific deductible and coverage details with your provider before you assume anything. We’ve put together more detail on cost and coverage questions on our glass repair FAQ page, which is worth a look before you call your insurer.

When your window is broken, every hour matters. An open pane invites rain, humidity, and even more debris into your home, especially with more storms forecast this week. A same-day repair from a local glazier means your home is secure again before the next round of severe weather hits.