Ontario's latest summer 2025 forecast calls for hotter than normal temps

Although the official start of summer is less than three weeks away, it certainly doesn't feel like it. The first week of June has unexpectedly kicked off with cool temperatures and a soggy forecast that's rather unusual for this time of year. 

However, don't be fooled by all the showers this week. Experts say this is just a slow start to what's expected to be a hotter-than-normal summer across Ontario. 

According to Environment and Climate Change Canada's (ECCC) latest 1-3 month outlook, Ontario residents should brace for a warm summer stretching from June through August 2025. 

Source: ECCC.

The southern half of the province, including cities like Toronto, Ottawa, and London, sits squarely in a 70 to 90 per cent probability zone for above-average temperatures over the next three months. 

Released this past Saturday, ECCC's seasonal forecast shows that the entire country is expected to sizzle under warmer-than-usual temperatures this summer, from the Maritimes all the way to British Columbia. In some regions, particularly eastern Canada and northern Ontario, the odds of warmer weather this upcoming season soar to nearly 100 per cent. 

The map aligns with The Weather Network's summer 2025 forecast, which also anticipates a hotter season than usual across most of Canada, including Ontario.

For those of us in southern and eastern Ontario, the heat is expected to be accompanied by higher-than-normal humidity. Although early June may feel unsettled, experts say the shift to summer-like conditions is on the horizon, and a heat wave before Canada Day isn't out of the question. 

According to The Weather Network's forecast, highs during the day are set to hover around normal or slightly above, and thanks to elevated humidity levels, nights are expected to also remain warm and sticky. 

The only downside is that this humidity will likely fuel more frequent showers and thunderstorms. While total precipitation is expected to be near or above seasonal norms, there will be plenty of sunny and dry weather to go around. 

In northern Ontario, however, the story is a bit more complex. Western areas of the region (communities west of Lake Superior, such as Thunder Bay) are set to experience a hot and dry summer, while areas east of Lake Superior (including Sudbury) will also see above-average temperatures, but with more humidity. 

The big concern for the north is the heightened risk of wildfire. As seen in 2023, smoke from distant fires can travel far and degrade air quality in cities like Toronto for days or even weeks. 

"If this threat is realized, the fires could have a far-reaching impact on other parts of the country," notes The Weather Network.

Overall, experts from both ECCC and The Weather Network seem to agree that the next three months are shaping up to be hotter than usual. So, while Ontario's summer may have gotten off to a cool and rainy start, you can expect to pull out your sunscreen and shades very soon.