If you’re looking forward to lots of outings with your partner, check out these details about year-round temperatures in Riobamba: The hottest months are usually October and November with an average temp of 52°F, while the coldest months are August and September with an average of 50°F. The rainiest months in Riobamba are April, March, February, and January, with each month seeing an average of 22 inches of rainfall.