Weather will likely play an important role when you plan your trip to Ascona, but bear in mind that cheaper options are usually available when the weather isn’t as good. 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 rainiest months in Ascona are August, October, May and November, with each month seeing an average of 211 mm of rainfall.