The temperature here's approx 2-5 degrees lower than in Phuket and the precipitation is just half. The fact that the temperature is lower is a good thing as it can be very hot in Thailand. The yearly average in the province is 82 degrees, which is more than enough.
There is three seasons. The warm season that is March to middle of May when it's very hot, 77-93 degrees, and very little precipitation. The rainy season is from May to October when it's a bit cooler, 75-90 degrees, and the precipitation is abundant. This is not as horrible as it sounds as where not talking dripping for days in a row. Instead there is powerful rainfalls and in between them often nice weather. But if you mainly want to sunbath you should avoid September-October when it rains the most. The third season that is the most pleasant, the cool season, is in November to February when there is almost no precipitation and temperature is between 70-90 degrees.
In short, if you can stand a bit of rain now and then, which can be nice in the heat, you can come here any time, but if you are totally against rainfall in your vacation you should go here between November and april.