July is the hottest month of the year in Montana with beautiful summer weather. The average high temperatures in the state are 75°F (23.9°C) to 88°F (31.1°C) and the night temperatures average 40°F (4.4°C) to 55°F (12.8°C). July is a little damp, but the rain is usually light and in the 1" (25mm) to 2" (51mm) range. Sunshine is the general norm everywhere, yet the temperatures are moderate, and it is rare for any place to see the mercury column touch 100°F (37.8°C). Thunderstorms sometimes happen in July, but they are mostly of the dry type and occur mainly in the eastern portion of Montana. Keep in mind, particularly in the highlands and mountain ranges, that temperatures plummet during the night, so keep warm clothes when camping in the mountains and national parks. Higher altitude valleys like the Big Hole River valley and West Yellowstone see freezing temperatures in the night even with high summer day temperatures!