Ontario to see very different winter from 'supercharged' El Niño

You've likely already seen headlines warning that a "supercharged" or "supersized" El Niño is on the way, but what exactly is El Niño, and what could the powerful climate phenomenon mean for Ontario's fall and winter?

According to an update from the World Meteorological Organization (WMO), El Niño is now firmly established and is expected to intensify into a "very strong event" in the coming months, with forecasts showing a 100 per cent likelihood that it'll persist through February 2027.

While it directly translates to "little boy" in Spanish, El Niño is actually a natural climate phenomenon characterized by unusually warm ocean surface temperatures in the central and eastern equatorial Pacific.

It typically occurs every two to seven years and lasts between nine and 12 months, but its effects can be felt thousands of kilometres away, as it significantly alters global atmospheric circulation and shifts temperature and precipitation patterns worldwide.

🌡️ El Niño is firmly established and will intensify into a very strong event in the coming months. WMO forecasts show ~100% likelihood that it will persist through February 2027.

A very strong El Niño ≠ same impacts everywhere.

🆕 WMO El Nino Update: https://t.co/KUPq04jjkT pic.twitter.com/PAx1EZTCOH

— World Meteorological Organization (@WMO) September 3, 2026

El Niño usually begins developing between March and June and reaches its peak intensity between November and February. Its impact on global temperatures can be the most pronounced in the year following its development.

The current El Niño began emerging in late spring and is continuing to build, with "exceptionally warm tropical Pacific Ocean conditions" supporting further intensification, according to the WMO. This climate pattern is known to fuel extreme weather worldwide, increasing the risk of floods, droughts, and extreme heat.

"El Niño is being supersized before our eyes. The science leaves no room for doubt: the planet is in uncharted waters, and those waters are heating up. Sea surface temperatures are rising, temperatures keep climbing, and the world is in the danger zone of extreme weather," said UN Secretary-General António Guterres.

"The race now is between rising risks and our commitment to take climate action and protect people. We must win that race."

As the WMO notes, sea surface temperatures across the central-eastern equatorial Pacific are already well above average. Between September and November 2026, WMO forecasts show an increased likelihood of above-normal temperatures across most land areas.

So what could the current El Niño mean for Ontario this fall and winter?

Although El Niño is often associated with warmer winters across Canada, its influence on fall weather is quite a bit different, especially here in Ontario.

"A pronounced trough normally settles over Ontario, while a more dominant ridge covers the upper West Coast during these autumn months. That means cooler weather mostly in the East and warmer weather in the West, with the most extreme cold and warmth staying in the northern parts of Canada," The Weather Network wrote in a report last month.

Over the past 75 years, there have been seven strong El Niño patterns during the fall, with the last one occurring in 2023. According to The Weather Network, temperature data collecting during El Niño falls were below the 1950-2025 average for the season in the GTA, but October saw the largest difference, with mean temperatures averaging 1.3 C below normal.

As a result, there could be an earlier taste of winter. The average for Toronto to first see at least 0.2 centimetres of snow is Nov. 11, but during strong El Niño years, that date moves up to Nov. 3.

However, the biggest shift in weather could come when winter officially arrives. The cooler pattern that tends to develop over Ontario during strong El Niño autumns generally breaks by December, bringing a "late onset" to winter.

In Toronto, December temperatures during strong El Niño years averaged 2.6 C warmer than normal. Still, that doesn't mean Ontario will be free of snow or winter storms, as El Niño influences larger atmospheric patterns and can't determine the weather on any individual day.

But the potential impacts of this looming El Niño will undoubtedly extend far beyond what's observed here in Ontario. Scientists note that the climate pattern in 2023 resulted in 2024 being the hottest year on record, and WMO officials note that 2027 has the potential to break it.