Planning for the weather is a good way to make your trip to Arosa relaxing and enjoyable, especially when you’re splurging. The hottest months are usually July and August with an average temp of 50°F, while the coldest months are January and February with an average of 20°F. The snowiest months in Arosa are April, May, November, and January, with each month seeing an average of 5 inches of snowfall.