It is simple fact that Hua Hin enjoys some of the best weather of all popular tourist locations in Thailand. With it's own micro climate the region very seldom experiences extreme weather conditions and never any flooding. If you, like many visitors to Thailand during the low season, are concerned about being stranded at your hotel in locations such as Phuket, Krabi or even Koh Samui due to continuous rain fall, Hua Hin might be a good destination offering the highest probability of long sunny days. This is in part due to the area's signature mountains and rolling hills.
Even during the rainy season which lasts from middle or end May until end October there is a high probability you will enjoy much more sunshine than rain allowing you to enjoy the interesting attractions and many exciting things to do in the area. Rainy season and cool season is not synonymous though and when it has rained it is usually followed by high levels of humidity and hot days which can easily see temperatures of 30 degrees or even higher.
But even when it does rain you need not have a dull moment. Use this time to explore the town's day spa's and get pampered, have a delectable meal complimented with a good red wine at Hua Hin Hills, the local wine producing vineyard and estate, go play ten pin bowling or even go watch the latest movie in English.
November until end January sees the area's cooler season. Do not not confuse cooler with cold weather though. Temperatures can still hang around the 30 degree Celsius mark and a minimum temperature of approximately 25 degrees later in the evening. Welcome breezes and the odd shower, though few and far between, keep things more moderate than usual.
The area naturally also enjoy its peak tourist season during this time seeing even more expensive 5 star hotels in Hua Hin often filled to the brim, so if you want to visit during this time, book well in advance to secure your room. It is a festive time to be here with whole streets adorned with colourful Christmas decorations from beginning December. February, March especially and also April are hot and dry months seeing basically no rain and temperature the can push to mercury up to and even over 40 degrees Celsius.