Because of the Gulf Stream, winters in the Bahamas are fairly mild, about 10 degrees F/5 C warmer than in nearby Florida. The summers can be humid, rainy and warm (day temperatures reaching into the low 90s F/33 C), but are moderated by trade winds. High season is November to mid-April, when northerners trade in cold for balmy climates, but in recent years the summer season has strengthened, especially for the Florida and East Coast market.
Hurricane season is June-November, and most rain falls at that time. There really is no bad time to go, but take along at least a sweater during the winter. Average day temperatures in fall and spring are in the 70s-80s F/23-32 C, with nights in the 60s F/15-22 C. Winter temperatures can be about 10 degrees F/5 C cooler.