The winter average for Nassau is 33.7 degrees Fahrenheit, compared to a summer average of 72.7 degrees. In Suffolk, the winter average is 32.4 and summer average is 71.9 degrees.The Nassau area receives about 45 inches of rain, compared to 42 inches for Suffolk.ong Island has a climate that is very similar to other coastal areas of the Northeastern United States; it has warm, humid summers and cold winters, but the Atlantic Ocean helps bring afternoon sea breezes that temper the heat in the warmer months and limit the frequency and severity of thunderstorms.