Planning for the weather is a good way to make your trip to Vang Vieng relaxing and enjoyable, especially when you're splurging. The hottest months are usually April and March with an average temp of 78°F, while the coldest months are January and December with an average of 69°F. The rainiest months in Vang Vieng are August, July, September, and June, with each month seeing an average of 15 inches of rainfall.