Planning for the weather is an important factor for making your trip to Isny im Allgaeu a success, especially when you’re splurging. The hottest months are usually July and August with an average temp of 60°F, while the coldest months are January and February with an average of 32°F. The rainiest months in Isny im Allgaeu are August, May, June, and July, with each month seeing an average of 7 inches of rainfall.