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 Tuen Mun: The hottest months are usually August and July, with an average temperature of 29°C, while the coldest months are January and December, with an average of 18°C. The rainiest months in Tuen Mun are August, June, May and July, with each month seeing an average of 326 mm of rainfall.