Forecasters say some of today's thunderstorms may pack a big punch, with winds strong enough to damage trees and power lines.

A rainfall warning has been issued for a wide swath of the Outaouais to the north and west of Gatineau, Que., while thunderstorm watches are in place elsewhere in the region.

Environment Canada has issued both a severe thunderstorm watch and a heat warning for the Montreal Island area, as dangerous heat and unstable weather take hold to start the week. Temperatures will soar to 32°C this afternoon,