Planning for the weather is a good way to make your trip to Klosters-Serneus relaxing and enjoyable, especially when you’re splurging. The hottest months are usually July and August with an average temp of 54°F, while the coldest months are January and February with an average of 24°F. The rainiest months in Klosters-Serneus are August, June, May, and July, with each month seeing an average of 8 inches of rainfall.