 Galveston 's climate is classified as humid subtropical ( <unk> in Köppen climate classification system ) . <unk> winds from the south and southeast bring both heat from the <unk> of Mexico and moisture from the Gulf of Mexico . Summer temperatures regularly exceed 90 ° F ( 32 ° C ) and the area 's humidity drives the heat index even higher , while nighttime lows average around 80 ° F ( 27 ° C ) . Winters in the area are temperate with typical January highs above 60 ° F ( 16 ° C ) and lows near 50 ° F ( 10 ° C ) . <unk> is generally rare ; however , 15 @.@ 4 in ( 39 @.@ 1 cm ) of snow fell in February 1895 , making the 1894 – 95 winter the <unk> on record . Annual rainfall averages well over 40 inches ( 1 @,@ 000 mm ) a year with some areas typically receiving over 50 inches ( 1 @,@ 300 mm ) . 
