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 Ushio Onsen: The hottest months are usually August and July, with an average temperature of 24°C, while the coldest months are January and February, with an average of 7°C. The rainiest months in Ushio Onsen are July, September, August and June, with each month seeing an average of 239 mm of rainfall.