If you're hoping to get lost in the rain on your romantic getaway, take a look at these details about year-round temperatures in Ruili: The hottest months are usually April and May, with an average temperature of 22°C, while the coldest months are January and December, with an average of 16°C. The rainiest months in Ruili are July, August, June and September, with each month seeing an average of 492 mm of rainfall.