If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Bellevue: The hottest months are usually August and July, with an average temperature of 18°C, while the coldest months are February and December, with an average of 5°C. The rainiest months in Bellevue are November, January, December and March, with each month seeing an average of 176 mm of rainfall.