If you’re hoping to get lost in the rain on your romantic getaway, check out these details about year-round temperatures in Val d’Illiez: The hottest months are usually July and August with an average temp of 57°F, while the coldest months are January and February with an average of 27°F. The rainiest months in Val d’Illiez are May, July, June, and December, with each month seeing an average of 8 inches of rainfall.