Weather will likely play an important role when you plan your trip to Montana, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually August and July, with an average temperature of 22°C, while the coldest months are January and February, with an average of 3°C. The snowiest months in Montana are November, January, December and February, with each month seeing an average of 18 cm of snowfall.