If you're looking forward to lots of outings with your partner, check out these details about year-round temperatures in Jianshui County: The hottest months are usually May and June with an average temp of 68°F, while the coldest months are January and December with an average of 54°F. The rainiest months in Jianshui County are August, July, June, and September, with each month seeing an average of 10 inches of rainfall.