A Guide to the Average Monthly Climate in Long Island, New York

Here's the inside skinny on temps and precipitation

Sunset near Cold Spring Harbor
••• Sunset near Cold Spring Harbor, New York. Benson Kua/Flickr/CC BY-SA 2.0

Whether you're planning a trip to Long Island, New York, or are a new resident, getting a handle on what to expect weather-wise is helpful when making plans, whether you are trying to decide when to go or thinking about weekend activities at home.

Long Island is divided into two counties: Nassau County to the west and Suffolk County on the eastern flank of the island. This doesn't include the boroughs of Brooklyn and Queens, which are geographically part of Long Island but politically part of New York City.

Both are on the eastern flank of Long Island.

Long Island is bordered by the East River, Long Island Sound, and the Atlantic Ocean.  Nassau County tends to be a bit warmer since it is closer to the mainland and more densely populated, causing a heat island effect. Suffolk County, besides being further from the mainland and less populated, benefits from breezes off the Atlantic and Long Island Sound, which moderate its summertime highs.

The beach-fringed island has four seasons: winter, spring, summer, and fall, with warm, sunny, somewhat humid summers and chilly winters. The area gets plenty of precipitation throughout the year. Below are the average temperatures for Long Island's two counties, according to U.S. Climate Data. Average precipitation is according to the Northeast Regional Climate Center.

These are average highs, lows, and precipitation amounts. When there's a heat wave or frigid cold front, the daily temperatures can deviate from these averages significantly.

This is also true for the precipitation that can result from severe storms in the summer, Noreasters, and heavy winter snowstorms. These temperatures and precipitation amounts should just be viewed as what's normal for the area in any given month and not a prediction of what the weather might actually be like on any given day in any given year.

All temperatures are in degrees Fahrenheit. 

Nassau County Average Temperatures
These average highs and lows are based on temperatures recorded at the weather station at Mineola, New York, in Nassau County.

  • January: high, 40; low, 26
  • February: 42; 28 
  • March: 50; 34
  • Apri:  60; 42
  • May: 70; 51 
  • June: 80; 61 
  • July: 85; 66
  • August: 83; 65
  • September: 76; 58
  • October: 65; 48
  • November: 55; 40
  • December: 45; 31

Suffolk County Average Temperatures
These average highs and lows are based on temperatures recorded at the weather station in Islip, New York, in Suffolk County.

  • January: high, 39; low, 23 
  • February: 40; 24
  • March: 49; 31
  • April: 58; 40
  • May: 69; 49
  • June: 77; 60
  • July: 83; 66 
  • August: 82; 65
  • September: 75; 57
  • October: 64; 45
  • November: 54; 36
  • December: 44; 28

Nassau County Average Precipitation
These numbers reflect the average precipitation at the weather station in Mineola, New York, in Nassau County

  • January: 4.01 inches
  • February: 2.96 inches
  • March: 4.28 inches
  • April: 4.26 inches
  • May: 4 inches
  • June: 3.66 inches
  • July: 3.88 inches
  • August:  3.74 inches
  • September: 3.98 inches
  • October: 3.53 inches
  • November:  4 inches
  • December:  3.80 inches

Suffolk County Average Precipitation
These numbers reflect the average precipitation at the weather station at Islip, New York, in Suffolk County. 

  • January: 4.27 inches
  • February: 3.33 inches
  • March: 4.76 inches
  • April: 4.13 inches
  • May: 3.90 inches
  • June: 3.71 inches
  • July: 2.93 inches
  • August: 4.48 inches
  • September: 3.39 inches
  • October: 3.63 inches
  • November: 3.86 inches
  • December: 4.13 inches