You'll likely spend much of your trip indoors, but if you're planning to venture beyond the casino, looking at local weather trends is a good idea. The hottest months are usually June and May with an average temp of 82°F, while the coldest months are January and February with an average of 75°F. The rainiest months in Nha Trang are November, October, December, and September, with each month seeing an average of 10 inches of rainfall.