Environment Canada has issued severe thunderstorm watches for almost all of western Quebec and some of Renfrew County Thursday afternoon and evening, noting a tornado could develop.
Forecasters also mention strong gusts of wind, large hail and heavy rain along with lightning.
The Outaouais exceptions are Gatineau, which almost always falls under the same alerts as Ottawa, and the Grenville-sur-la-Rouge area that commonly shares alerts with Montreal.
Environment Canada has been mentioning the possibility of tornadoes for eastern Ontario since Tuesday. The first alerts, for the Algonquin Park and Deep River areas, came around 11:45 a.m. Thursday. Gusts there could reach 110 km/h, according to the watch.
Environment Canada recommends staying indoors and taking cover in a basement where possible during these types of threatening weather, and notes strong winds can damage trees or buildings and overturn vehicles.
It issues a severe thunderstorm watch when conditions are favourable for a storm to develop. A warning is issued when there is evidence that a thunderstorm is imminent or occurring that will produce damaging hail, wind or rain.
Tornado watches and warnings follow a similar system.
A very hot Thursday is also expected, with Ottawa potentially reaching a high of 34 C that feels like 43 with humidity. That’s warning-worthy heat, but it won’t last long enough: Friday’s forecasted high for the capital is back to a seasonal 27 C.