What the next three months of fall weather will look like in Ontario

It's the first day of October, which means you've probably been reaching for your cozy sweaters already, but if you're a fan of warmer weather, you'll be pleased to hear that you might not have to rush out to pull out your winter jackets anytime soon. 

According to Environment and Climate Change Canada's (ECCC) latest probabilistic forecasts, Ontario has a strong chance of seeing above-normal temperatures this fall season. 

The federal department released its three-month forecast on Wednesday, offering an early look at temperature trends across the country between October and December 2026. ECCC's prediction system forecasts the evolution of meteorological trends over the coming season, but isn't designed to predict specific weather events, like storms or periods of heavy precipitation. 

For Ontario, the latest three-month outlook points overwhelmingly toward above-normal temperatures throughout the period. 

According to the first model, northern Ontario has between a 90 and 100 per cent chance of seeing above-normal temperatures between October and December. Meanwhile, most of southern Ontario, including the GTA, has a 70 to 80 per cent probability of temperatures coming in above normal. 

On the other hand, southwestern Ontario has a slightly lower probability (but still a majority chance) of 60 to 70 per cent. 

The next map shows the probability of near-normal temperatures throughout the period, and while most of Ontario has a 0 to 10 per cent chance, the GTA has a slightly elevated probability between 10 and 20 per cent. 

As for below-normal temperatures, the third model shows that all of Ontario (apart from a tiny sliver above Lake Erie) has between a 0 and 10 per cent chance of experiencing cooler-than-usual temperatures between October and December. 

Although seasonal forecasts can change, the current outlook is heavily swayed toward warmer-than-normal conditions across Ontario this fall, and there's a major climate pattern behind the shift. 

According to an update last month from the World Meteorological Organization (WMO), a "supersized" El Niño is expected to intensify over the next few months, with a 100 per cent likelihood that the climate event will persist through February 2027. 

The natural climate phenomenon is characterized by unusually warm ocean surface temperatures in the central and eastern Pacific, and its effects can be felt all the way across the world, including here in Ontario, as the pattern shifts temperature and precipitation patterns. 

El Niño's effects on fall might be cooler at first, but this pattern tends to break by December, resulting in a late onset of winter. 

According to The Weather Network, temperature data collected during strong El Niño falls were below the 1950-2026 average for the season in the GTA, and October saw the biggest difference, with mean temperatures averaging 1.3 C below normal. 

However, in Toronto, December temperatures during strong El Niño events have averaged 2.6 C warmer than usual.