GREENSTONE — National weather and public health officials are urging people across much of the Northwest to keep cool Friday.
Heat warnings were put into effect early Friday morning. They range from Atikokan in the west, east through Thunder Bay and extend well into northeastern Ontario. Communities right along the North Shore were spared, but the alerts include the Lake Nipigon area, Armstrong, the rest of Greenstone, Manitouwadge and Hornepayne.
Temperatures are expected to be around 29 C, with the humidity making it feel more like 36.
Crawford Luke, a meteorologist with Environment Canada, said a southerly flow of hot, humid air is coming up from the United States in between a low pressure system over Manitoba and a high pressure system over parts of Ontario, Quebec and the northeastern U.S.
“Definitely, the number one thing for any heat warning is to try to stay hydrated and stay cool,” Luke said. “So, making sure you're drinking a lot of water, staying hydrated, try to limit time outside if possible, especially during those peak midday hours when the sun's at its strongest and temperatures are hottest.”
Taking more frequent breaks or taking advantage, if possible, of things like air conditioning, swimming pools, a nearby lake, or “even just sitting under a tree,” are other options, he said.
“It's also very humid as well, which we don't always see in this part of the country,” he said. “So, the humidity is really there with this heat event as well.”
Eventually, Luke said, a cold front associated with the low pressure system from Manitoba will pass through the region, bringing in an air mass with a bit less humidity.
“We don't really cool off drastically, but we cool off by a few degrees,” he said.
In Northern Ontario, Luke said heat warnings are issued when there are two days in a row of daytime highs of at least 29 C with in-between overnight lows of at least 18 C, or having two days in a row with a humidex of 36 or higher.
Different regions have different criteria for the issuing of heat warnings — for example places like Toronto and Windsor have much higher thresholds.
“It's a combination of local climatology mixed with public health,” Luke said. “All these numbers were set in consultation with (the) Public Health (Agency of) Canada and the local public health units.”