If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Grundlsee: 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 30°F. The snowiest months in Grundlsee are December, January, November, and February, with each month seeing an average of 6 inches of snowfall.