London area braces for multi-day heat event starting Sunday

Londoners should be prepared for a stretch of sweltering heat beginning this weekend, with temperatures expected to climb above 30 C and feel even hotter with the humidex.

According to Environment Canada, a warm and humid air mass will move into the region on Sunday pushing daytime highs to the low 30s. With the humidity, it could feel closer to the low 40s. The heat is expected to stick around through at least Tuesday, with a chance of lingering into Wednesday or Thursday.

"This is what we call an extreme heat event," said Steven Flisfeder, a warning preparedness meteorologist with Environment Canada. "It's going to feel hot and sticky, and that's going to last for several days."

The forecast calls for a high of 33 C on Sunday and 34 C on both Monday and Tuesday. Overnight lows are expected to hover around 23 C, offering little relief, especially for people without air conditioning.

While a formal heat warning has not yet been issued as of Thursday at noon, Flisfeder said it's essential to take precautions.

"If you're particularly susceptible to heat, or know someone who is, it's important to limit outdoor activity, stay hydrated, and seek out air-conditioned or cooler spaces when you can," he said.

He also noted that muggy conditions can be challenging for people with respiratory conditions, even if wildfire smoke is not currently a factor in air quality.

The City of London has opened all of its outdoor spray pads, along with the Gibbons and Byron outdoor pools. When a heat alert is issued, the city also provides cooling centres at four community centres and the Central Library.

This heat comes after what has been a dry start to the summer. Flisfeder said southwestern Ontario has seen less rainfall than usual, though that could start to change. There's a 40 per cent chance of showers and a risk of thunderstorms on Friday, with the possibility of severe storms developing later in the day.

"The most likely threat will be strong winds," he said. "But hail and tornadoes are also possible, just to a lesser degree."

Environment Canada is advising people to keep an eye on updated forecasts, drink plenty of water, and check in on neighbours or loved ones who may be more vulnerable.