If you’re hoping to get lost in the rain on your romantic getaway, take a look at these details about year-round temperatures in Uster: The hottest months are usually July and August, with an average temperature of 16°C, while the coldest months are February and January, with an average of 1°C. The rainiest months in Uster are August, June, July and May, with each month seeing an average of 214 mm of rainfall.