West and northwest Montana (such as Missoula, Helena, Great Falls and Havre) are under a Heat Advisory for Tuesday through Friday (7/2). Counties that don't already have some sort of advisory in effect may get their own in the coming days as very high temps are on their way.
Temps over 100 degrees will be common for most of the NE quarter of Montana on Wednesday. (Glasgow, Wolf Point, Malta, Plentywood, Sidney.) The Heat Advisory lasts until at least 9pm on Wednesday evening.