ATLANTIC CANADA - Hot, steamy weather has prompted Canada's national weather forecaster to issue heat warnings for the Maritimes as well parts of both Ontario and Quebec.

Environment Canada says a very warm and humid air mass will move into the Maritimes today and stay until Thursday. Humidex values could reach 42 C in some areas.

Tuesday could be even warmer, but some relief from the heat is expected by Thursday.

In southern Ontario and Quebec, the humidex is also likely to hit the low 40s today, however, forecasters say cooler air is expected to move into parts of Ontario this evening, bringing an end to what has been a nearly weeklong heat event.

Parts of western Canada are also expected to heat up today, with Environment Canada predicting daytime highs in the 30 degree range through till Friday.

Meanwhile, a high pressure ridge is building over coastal British Columbia, and temperatures there are also expected to reach into the low 30s.