If you're looking forward to lots of outings with your partner, check out these details about year-round temperatures in Chengkan: The hottest months are usually August and July with an average temp of 77°F, while the coldest months are January and December with an average of 44°F. The rainiest months in Chengkan are June, July, May, and April, with each month seeing an average of 11 inches of rainfall.