Like the rest of Thailand, Pattaya is subject to the annual monsoon rains, which are heaviest from May through October. The coolest and driest time of year is December and January. While I generally emphasize that the rainy season is not an entirely bad time to visit Thailand, it really isn't a good time to visit Pattaya. There is very little to do away from the beaches, since there are no historical or cultural attractions in the area. Even the shopping isn't all that good. See the banner below for current conditions.

Current conditions (as of 1:00 PM)

Cloudy. 31°C (Feels like 32). Humidity: 53% Winds: 11 km/hr NE.
All times shown are local to Pattaya, THA.
Detailed ten-day forecast   Hourly weather forecast    Weather maps    Weather averages

Today: AM Rain. Lo: 24°C. Hi: 33°C. Chance of precipitation: 80%
Tomorrow: Clear. Lo: 24°C. Hi: 35°C. Chance of precipitation: 5%
Friday: Clear. Lo: 25°C. Hi: 36°C. Chance of precipitation: 5%
Saturday: Clear. Lo: 26°C. Hi: 35°C. Chance of precipitation: 5%
Sunday: T-storms. Lo: 27°C. Hi: 34°C. Chance of precipitation: 45%

More information at MSN Weather
(Data provided outside US and Canada by Foreca, Data provided for US and Canada by WDT)