Islip, New York climate: Normal weather by month, frost dates and records
Islip's normal year runs from 25°F January nights to 83°F July afternoons, with 46.0 inches of precipitation and 32 inches of snow a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 11.7°C, January lows of −4°C, July highs of 28°C, 1,168 mm of precipitation a year.
- NOAA stationIslip-Li Macarthur Airport
- Station IDUSW00004781
- Location40.79°N 73.10°W
- Elevation84 ft (26 m)
- From the center7 miles
- Population (census place)17,224
On October 14, the normal high in Islip is 65°F and the normal low 48°F, and the chance of measurable rain or snow is 30%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Islip.
- Jan 39° 25°
- Feb 41° 26°
- Mar 48° 32°
- Apr 58° 41°
- May 68° 51°
- Jun 77° 61°
- Jul 83° 67°
- Aug 81° 66°
- Sep 75° 59°
- Oct 64° 47°
- Nov 54° 38°
- Dec 44° 30°
Each month: normal high (large) and low, °F. Fill: the month's normal mean, colder blue to hotter red.
What is the weather like in Islip each month?
July is the warmest month, with normal highs of 83°F; January the coldest, with normal lows of 25°F. The most precipitation falls in December (4.71 in), the least in July (3.26 in).
| Month | High | Low | Mean | Precip. | Snow | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|---|
| January | 39°F | 25°F | 31.9°F | 3.66 | 10.3 | 11 | <1 | 25 | 9 h 30 min |
| February | 41°F | 26°F | 33.3°F | 3.29 | 9.4 | 10 | <1 | 22 | 10 h 40 min |
| March | 48°F | 32°F | 39.9°F | 4.51 | 6.5 | 11 | <1 | 17 | 11 h 50 min |
| April | 58°F | 41°F | 49.7°F | 4.06 | 0.6 | 11 | <1 | 3 | 13 h 20 min |
| May | 68°F | 51°F | 59.5°F | 3.28 | 0.0 | 12 | <1 | <1 | 14 h 30 min |
| June | 77°F | 61°F | 69.0°F | 4.00 | 0.0 | 10 | 2 | <1 | 15 h |
| July | 83°F | 67°F | 75.0°F | 3.26 | 0.0 | 9 | 4 | <1 | 14 h 50 min |
| August | 81°F | 66°F | 73.7°F | 4.24 | 0.0 | 9 | 2 | <1 | 13 h 50 min |
| September | 75°F | 59°F | 66.9°F | 3.60 | 0.0 | 9 | <1 | <1 | 12 h 30 min |
| October | 64°F | 47°F | 55.7°F | 3.97 | 0.0 | 9 | <1 | 1 | 11 h 10 min |
| November | 54°F | 38°F | 45.6°F | 3.41 | 0.5 | 10 | <1 | 9 | 10 h |
| December | 44°F | 30°F | 37.1°F | 4.71 | 4.5 | 12 | <1 | 21 | 9 h 20 min |
| Year (annual) | 61°F | 45°F | 53.1°F | 45.99 | 31.8 | 122 | 8 | 98 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. | Snow |
|---|---|---|---|---|---|
| January | 4°C | −4°C | −0.1°C | 93 mm | 26 cm |
| February | 5°C | −4°C | 0.7°C | 84 mm | 24 cm |
| March | 9°C | 0°C | 4.4°C | 115 mm | 17 cm |
| April | 15°C | 5°C | 9.8°C | 103 mm | 2 cm |
| May | 20°C | 10°C | 15.3°C | 83 mm | 0 cm |
| June | 25°C | 16°C | 20.6°C | 102 mm | 0 cm |
| July | 28°C | 20°C | 23.9°C | 83 mm | 0 cm |
| August | 27°C | 19°C | 23.2°C | 108 mm | 0 cm |
| September | 24°C | 15°C | 19.4°C | 91 mm | 0 cm |
| October | 18°C | 8°C | 13.2°C | 101 mm | 0 cm |
| November | 12°C | 3°C | 7.6°C | 87 mm | 1 cm |
| December | 7°C | −1°C | 2.8°C | 120 mm | 11 cm |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00004781; annual normals. Wet days: 0.01 inch or more; 90°F days and freezing nights: NOAA's day counts. Daylight: sunrise to sunset on the 15th, computed from the latitude.
When is the best weather to visit Islip?
Normal highs sit between 65°F and 85°F in May, June, July, August and September. Of those, September has the fewest days with rain (9).
That is a measurement, not a recommendation: it counts the months whose normal afternoon high sits between 65°F and 85°F, where a light layer is enough by day.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00004781.
When is the last frost in Islip?
In Islip, the last spring frost (32°F) comes after April 10 in half of years and after April 25 in one year in ten; the first autumn frost comes before November 2 in half of years and before October 18 in one year in ten.
Frost-free in half of yearsFrost in 1 to 9 years out of 10Frost most years
- Last spring frost, half of years after
- April 101 year in 10 after April 25; 9 in 10 after March 31
- First autumn frost, half of years before
- November 21 year in 10 before October 18; 9 in 10 before November 15
NOAA puts the median frost-free season at 207 days, and the season without a hard freeze (28°F) at 230 days.
A hard freeze (28°F) comes after March 30 in half of springs and before November 14 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Islip in zone 7b in ZIP code 11751. By the map's own method, the average of each year's coldest night over 1991-2020, Islip's NOAA station is in zone 7b: the coldest night of a typical year reaches 5°F (30 complete years).
Frost dates for every NOAA station in New York · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00004781; USDA 2023 Plant Hardiness Zone Map, ZIP listings: PRISM Group, Oregon State University, https://prism.oregonstate.edu, accessed October 8, 2026; the station zone: ACIS daily lows, 1991-2020. A 10% date means one year in ten has a frost after it in spring or before it in autumn.
How hot and how cold does it get in Islip?
In a normal year in Islip, 8 days a year reach 90°F, 98 nights fall to 32°F or colder and 122 days bring measurable precipitation.
- Days at 90°F or more
- 8a normal year
- Days at 100°F or more
- fewer than 1a normal year
- Nights at 32°F or colder
- 98a normal year
- Days that stay below freezing
- 16high of 32°F or less
- Days with 0.01 inch of precipitation
- 122a normal year
- Days with 1 inch of snow or more
- 8a normal year
The highest temperature in Islip's official record (kept by the National Weather Service since 1963) is 104°F, on July 3, 1966; the lowest is −14°F, on February 13, 1967.
The wettest calendar year on that record is 1989, with 65.32 in; the snowiest season is 1995–96, with 77.1 inches.
Source: NOAA NCEI 1991-2020 annual normals, station USW00004781; records: ACIS (NOAA Regional Climate Centers), NWS threaded record ISPthr. Records use complete months only; a month missing more than three days is left out.
How sunny is Islip?
Over a year 75% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Islip, 4.0 kWh per square metre a day. July is the sunniest month (82%) and December the cloudiest (66%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 67% | 1.9 |
| February | 70% | 2.8 |
| March | 71% | 3.8 |
| April | 73% | 5.0 |
| May | 73% | 5.6 |
| June | 78% | 6.1 |
| July | 82% | 6.2 |
| August | 81% | 5.5 |
| September | 79% | 4.5 |
| October | 72% | 3.0 |
| November | 72% | 2.1 |
| December | 66% | 1.6 |
Source: NASA POWER solar climatology, 2001-2020 (CERES SYN1deg). Satellite-based, for the 1-degree cell (about 100 km across) around the station, so it describes the area rather than the airport.
How much heating and cooling does Islip need?
A normal year in Islip brings 5,183 heating degree days, 4% fewer than the median U.S. place (5,373), and 885 cooling degree days, 2% fewer than the median (908). Seven months need 300 or more heating degree days, a monthly mean of about 55°F or colder. For gardens and crops, NOAA counts 3,242 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,026 | 0 |
| February | 889 | 0 |
| March | 780 | 0 |
| April | 460 | 3 |
| May | 196 | 27 |
| June | 30 | 152 |
| July | 1 | 312 |
| August | 2 | 271 |
| September | 53 | 108 |
| October | 301 | 13 |
| November | 582 | 0 |
| December | 865 | 0 |
| Year (annual) | 5,183 | 885 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00004781. A degree day is one degree of a day's mean temperature below 65°F (heating) or above it (cooling); utilities use them to estimate energy use.
Has Islip been warmer than normal lately?
2025 averaged 54.7°F, 1.6°F above the 1991-2020 normal of 53.1°F. 5 of the 5 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. | Snow |
|---|---|---|---|---|
| 2021 | 54.7°F | +1.6°F | 46.40 | 26.3 |
| 2022 | 54.3°F | +1.2°F | 39.61 | 37.1 |
| 2023 | 55.4°F | +2.3°F | 50.19 | 4.6 |
| 2024 | 55.2°F | +2.1°F | 48.80 | 13.0 |
| 2025 | 54.7°F | +1.6°F | 36.91 | 22.1 |
Over 58 complete years from 1964 to 2024, the station's annual mean temperature rose at a fitted 5.6°F per century (+0.31°C per decade). A fitted rate summarizes the whole record; single years swing well above and below it.
Source: observed years: ACIS, station USW00004781; trend: NOAA GHCN-Monthly v4. A year counts only with all twelve months complete.
How does Islip's climate compare?
Islip is warmer than 121 of the other 130 places with their own NOAA record in New York, and wetter than 82. Across the 7,247 U.S. stations with normals, its annual mean of 53.1°F is warmer than 54%.
In the Köppen classification computed from these normals, Islip is Dfa: continental, no dry season, hot summer. What the classes mean.
Places with the most similar year elsewhere
Measured month by month on the normal high, low and precipitation, among places of 20,000 or more people in other states:
Source: NOAA NCEI 1991-2020 normals for every station PlainClimate covers. Similarity: the root-mean-square difference of the 36 monthly figures, precipitation weighted so an inch counts like 6°F.
Which places near Islip share this climate record?
19 places have no NOAA station with 1991-2020 normals of their own, and this station is the nearest full record. A place's own climate can differ from these figures, by several degrees where it sits much higher or lower than the station, nearer the coast, or inside a large city's heat; for the larger places the next nearest records are named with their yearly mean, so the spread around them is visible, and places of 50,000 or more have their own page with NOAA's gridded normals.
- Central Islip, NY37,751 people · 5 mi W
- Centereach, NY31,501 people · 5 mi N
- Holbrook, NY26,256 people · 2 mi E
- Smithtown, NY24,940 people · 7 mi NW
- East Patchogue, NY21,364 people · 6 mi E
- Hauppauge, NY20,772 people · 6 mi W
- Holtsville, NY19,250 people · 3 mi NE
- Ronkonkoma, NY18,368 people · 1 mi NW
- Lake Ronkonkoma, NY18,289 people · 3 mi N
- Farmingville, NY16,605 people · 4 mi NE
- Nesconset, NY13,344 people · 5 mi NW
- Lake Grove, NY11,109 people · 4 mi N
- Bohemia, NY9,306 people · 2 mi SW
- North Patchogue, NY7,243 people · 4 mi E
- Islip Terrace, NY5,223 people · 5 mi SW
- Islandia, NY3,651 people · 4 mi W
- North Great River, NY3,638 people · 4 mi SW
- Village of the Branch, NY1,763 people · 6 mi NW
- Brentwood, NY8 mi W
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
Questions about Islip's climate
What is the coldest month in Islip?
January, with a normal high of 39°F and a normal low of 25°F. The warmest is July (83°F by day, 67°F at night).
Does it snow in Islip?
Yes: 32 inches in a normal year, falling on 13 days with 0.1 inch or more, the most in January (10.3 inches).
What is the rainiest month in Islip?
December, with 4.71 in of precipitation in a normal year; the driest is July with 3.26 in.
What plant hardiness zone is Islip in?
The USDA's 2023 map puts Islip in zone 7b in ZIP code 11751. By the same method at Islip's NOAA station, the coldest night of a typical year reaches 5°F (30 years, 1991-2020): zone 7b.
How late can frost come in Islip?
In half of years the last 32°F night comes after April 10; in one year in ten it comes after April 25. Waiting until April 25 leaves about a one-in-ten chance of a later frost.
Nearby and next
- New York climateThe statewide normals and every place in the state
- Molloy Cercom, NY5 miles from this station, 53.1°F a year
- Mount Sinai, NY11 miles from this station, 54.7°F a year
- Setauket, NY11 miles from this station, 53.4°F a year
- Shirley, NY12 miles from this station, 52.4°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made