Planning for the weather is a good way to make your trip to Grundlsee relaxing and enjoyable, especially when you’re splurging. The hottest months are usually July and August, with an average temperature of 15°C, while the coldest months are January and February, with an average of -1°C. The snowiest months in Grundlsee are December, January, November and February, with each month seeing an average of 15 cm of snowfall.