Planning for the weather is a good way to make your trip to Tainan relaxing and enjoyable, especially when you’re splurging. The hottest months are usually July and August, with an average temperature of 29°C, while the coldest months are January and February, with an average of 20°C. The rainiest months in Tainan are August, June, May and July, with each month seeing an average of 418 mm of rainfall.