If you're looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Riobamba: The hottest months are usually October and November, with an average temperature of 11°C, while the coldest months are August and September, with an average of 10°C. The rainiest months in Riobamba are April, March, February and January, with each month seeing an average of 566 mm of rainfall.