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 Jiujiang: The hottest months are usually August and July, with an average temperature of 25°C, while the coldest months are January and December, with an average of 6°C. The rainiest months in Jiujiang are June, July, May and April, with each month seeing an average of 306 mm of rainfall.