Planning for the weather is a good way to make your trip to Treffen relaxing and enjoyable, especially when you’re splurging. The hottest months are usually July and August, with an average temperature of 17°C, while the coldest months are January and February, with an average of 0°C. The rainiest months in Treffen are August, July, May and September, with each month seeing an average of 196 mm of rainfall.