Planning for the weather is a good way to make your trip to Val d’Illiez relaxing and enjoyable, especially when you’re splurging. The hottest months are usually July and August, with an average temperature of 14°C, while the coldest months are January and February, with an average of -3°C. The rainiest months in Val d’Illiez are May, July, June and December, with each month seeing an average of 202 mm of rainfall.