If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Steindorf am Ossiacher See: The hottest months are usually July and August with an average temp of 62°F, while the coldest months are January and February with an average of 31°F. The rainiest months in Steindorf am Ossiacher See are August, July, May, and September, with each month seeing an average of 8 inches of rainfall.