Hot summer, above-normal temperatures ahead for southern Ontario

Extreme weather is making the headlines once again, with a tornado ripping through Barrie last Thursday and causing damage to 25 homes.

Meanwhile, northwestern Ontario is experiencing dry conditions that have led to an early forest-fire situation, as hundreds of hectares burn in that quadrant of the province.

What’s in store for the province for the remainder of the summer remains to be seen — but Ontario and much of the country can expect temperatures that are higher than normal. That’s the prediction from Environment Canada, which shows a high probability of above-normal temperatures in areas of the province surrounding the Great Lakes, as well as B.C., and into parts of Eastern Canada. The forecast also shows a good chance of abovenormal temperatures in the rest of the country.

The active storm track that has already hit southern Ontario is part of the thousands of thunderstorms that we can expect during the period that runs from late April into early October, bringing with it the possibility of 12 to 14 tornadoes on average.

“The big trigger for us is when we start to get the hot, humid air masses coming northward from the Gulf of Mexico, “said Geoff Coulson, a warning preparedness meteorologist with Environment Canada. “That low-level humidity is the fuel that drives thunderstorm formation. And when some other factors come together, that can sometimes lead to the development of severe thunderstorms, which have the capability of producing tornadoes in addition to damaging hail, strong winds and flash floods.”

Mercury climbing

“The big story provincewide for the forecast is a continuation of the warm-weather temperatures, “said Coulson. “And the forecast models seem to be saying this in general across the province.”

The models don’t show how much above normal the temperature will be.

“The second half of July and the first part of August is traditionally our warmest time of the year, where daytime highs can routinely get up into the high 20s, “said Coulson. “So if the models are indicating warmer than normal, the implication would be we could see more 30-plus degree days during the second half of July, the first week of August.”

In terms of precipitation, there is no strong trend in southern Ontario, he said, but the models are indicating that northwestern Ontario is expected to remain drier than normal, a concern since the forest fire season in that region has started early this year.

Rainfall over Great Lakes

This year, the months of March, April and May were the driest on record in the Great Lakes Basin since 1965, said Frank Seglenieks, the Canadian secretary of the Lake Ontario-St. Lawrence River Board, which manages outflows from Lake Ontario.

This is the result of global weather patterns, he said, where some high-pressure zones around the Great Lakes deflected the jet stream, which can pull storms along with it.

Drought in the Basin

Water levels in Lake Ontario are down an average of about 30 centimetres due to the drought conditions. The upper Great Lakes — Superior, Michigan, Huron and Lake Erie — haven’t been impacted as much by the drought because of record high water levels in the years leading up to 2020, when Michigan and Huron water levels were about a metre higher than normal.