If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Locarno: 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 Locarno are August, October, May and November, with each month seeing an average of 211 mm of rainfall.