MONTREAL -- As a heat warning continues for the Montreal area, with Humidex values expected to hit 40C Monday afternoon, Environment Canada is now warning of severe thunderstorms, too.

The agency issued the warning for the Montreal Island, Laval, Chateauguay-La Prairie and Longueuil-Varennes areas.

Environment Canada says weather conditions "are favourable for the development of severe thunderstorms that may be capable of producing strong wind gusts, large hail and heavy rain" on Monday afternoon and evening.

The agency warns that sudden and heavy downpours could cause flash flooding and pooling of water on roads and highways.