Hot and unsettled weather on the way for Waterloo region, Guelph and Wellington County

Expect hot and unsettled weather for the rest of the work week in Waterloo region, Guelph and Wellington County.

A heat warning has been issued by Environment and Climate Change Canada as hot and humid conditions are expected to start Wednesday in much of southern Ontario.

The forecast is calling for:

Nighttime won't bring much relief from the heat with minimum temperatures expected in the low 20s, the heat warning said.

Gerald Cheng is a meteorologist with Environment and Climate Change Canada and says the weather this week will throw "every type of summer weather" at the region.

It's "a very typical summer day when we have to deal with heat and humidity, and with that comes thunderstorms," he told CBC News.

Cheng said there's a southwesterly flow that's setting up over southwestern Ontario that is bringing the hot temperatures and humidity. He said people should be prepared for thunderstorms. 

"Thunderstorms, they can develop quite quickly and conditions can change in an instant," he said, noting people going out for a walk or hike should definitely keep an eye on the skies in the coming days.

"It's really important to be aware of our surroundings because conditions can change so quickly, especially when we want to enjoy the great outdoors nowadays," Cheng said.

"Thunderstorms are very different from snowstorms or huge systems where we get the same types of weather, whether we are traveling to Guelph or whether we go southwest to London," he said.

But he noted thunderstorms can be very isolated, "so it may rain lots in our neighbourhood and then the next one over has nothing."

The hot weather is expected to subside on the weekend, with a high of 24 C predicted for Saturday with a chance of showers.

The Region of Waterloo has designated cooling centres at its offices at 150 Main St. in Cambridge, 150 Frederick St. in Kitchener, which are both open seven days a week, and 99 Regina St. S. in Waterloo, which is open during regular business hours Monday to Friday.

Other places to cool off include local libraries and some community centres. More information can be found on the region's website.