If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Fiesch: The hottest months are usually July and August with an average temp of 47°F, while the coldest months are January and February with an average of 18°F. The rainiest months in Fiesch are July, August, June, and May, with each month seeing an average of 7 inches of rainfall.