Photo: DanTD · CC BY-SA 3.0July in Islip stays fresher than in 72% of U.S. towns
January nights here settle around 26°. A year here swings 57° from midwinter lows to midsummer highs. Winters are mild: January nights here are milder than in 64% of U.S. towns. The outdoor season runs from May to October, with highs of 65–83°.
A year in Islip at a glance
Each month’s typical high and low, and what it brings.
What stands out about Islip’s climate
Compared with towns across the U.S., with Islip’s place in New York beside it.
What a year in Islip feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 207 frost-free days a year
In half of years the last 32° night comes by April 10 and the first by November 2. Frost and day counts come from Islip Li Macarthur Airport, Islip’s official weather station (the one in National Weather Service reports), 7 miles from the city’s center point, at about the same height.
The 2023 USDA map puts Islip’s center in zone 7b: the coldest night of a typical winter, averaged over 1991–2020, reaches about 7°. Plant labels use the zone; frost dates tell you when to plant.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
About 32 inches of snow a winter
Snow, measured at Islip Li Macarthur Airport, is heaviest from January through February, about 10 inches a month. Precipitation (rain plus melted snow) adds up to 45 inches a year; December is the wettest month and February the driest. Rain or snow falls on about 122 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
Heating and cooling a home in Islip
85% of the work is heating, so the furnace matters far more than the air conditioner. Months averaging under 55° run from November through April.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. NOAA normals at Islip Li Macarthur Airport.
Living with Islip’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
207 frost-free days in zone 7b. The last frost comes by Apr 10 in half of years, so many gardeners wait a week or two past that to set out tomatoes. The first fall frost comes by Nov 2.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August, September and October. 137 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Islip from natural hazards, river flooding is the largest share (55%); heat waves, cold waves, winter storms and ice storms together are 9%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Islip and its neighbors
Brookhaven has the coldest January nights next door (23°, 3° colder). Differences under a degree are within what the 5 km grid can tell apart. Tap a town to see its climate.
Climates most like Islip’s, farther away
TownRatings’ own comparison of NOAA 1991–2020 normals, not a NOAA product: places of 5,000+ at least 150 miles away, one per state, closest on January low, July high, precipitation and snow.
| Town | Jan. low | July high | Precip. | Snow |
|---|---|---|---|---|
| Islip, NY | 26° | 83° | 45" | 32" |
| Blacksburg, VA | 25° | 84° | 43" | 25" |
| Uniontown, PA | 22° | 84° | 45" | 28" |
| Mount Airy, MD | 24° | 85° | 46" | 31" |
| Fairmont, WV | 23° | 84° | 46" | 24" |
Temperatures and rain come from NOAA’s 5 km grid, so each town gets its own value. Snow and frost-free days come from the nearest weather station, so neighbors often share them.
Warmer than it used to be
The last 30 years in Islip averaged 2.3° warmer than the 1900s. The biggest change is in December (+3.7°).
A bigger shift than in 98% of U.S. towns.
Change by month
The two periods overlap (1991–2000 is in both), which makes the gap a little smaller than it would be between separate periods. In a city of 341,000 people, part of the change is the city itself: pavement and buildings hold heat (the urban heat island).
How Islip compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Islip’s place among New York’s.
Islip weather by month
Highs, lows and precipitation from NOAA’s grid at Islip’s center; snow, wet days and snow on the ground from Islip Li Macarthur Airport. 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 40° | 26° | 3.4" | 10.3" | 11 | 7 | 25° – 39° |
| February | 42° | 26° | 3.1" | 9.4" | 10 | 9 | 22° – 40° |
| March | 48° | 33° | 4.3" | 6.5" | 11 | 4 | 36° – 48° |
| April | 59° | 41° | 3.9" | 0.6" | 11 | 0 | 46° – 54° |
| May | 68° | 51° | 3.4" | 0.0" | 12 | 0 | 55° – 64° |
| June | 77° | 60° | 3.9" | 0.0" | 10 | 0 | 66° – 73° |
| July | 83° | 67° | 3.4" | 0.0" | 9 | 0 | 70° – 79° |
| August | 82° | 66° | 3.9" | 0.0" | 9 | 0 | 70° – 78° |
| September | 75° | 60° | 3.9" | 0.0" | 9 | 0 | 65° – 72° |
| October | 65° | 48° | 4.1" | 0.0" | 9 | 0 | 52° – 63° |
| November | 54° | 39° | 3.5" | 0.5" | 10 | 0 | 41° – 51° |
| December | 45° | 31° | 4.4" | 4.5" | 12 | 3 | 31° – 50° |
| Year | 62° | 46° | 45.1" | 31.8" | 122 | 23 |
How much a month can swing
A normal is an average. December swings the most: from 1991 to 2020 its average ranged from 31° to 50°. June is the most reliable, staying within 7°.
Where Islip’s numbers come from
Normals are 30-year averages, not a forecast. How TownRatings reads climate data →
- Temperatures and precipitation: NOAA’s gridded 1991–2020 normals for the 5 km cell at Islip’s center.
- Snow: Islip Li Macarthur Airport (the official station).
- Frost, freezing nights, 90° and 100° days, heating and cooling: Islip Li Macarthur Airport, 7 miles from the city’s center point, at about the same height; the city’s official station.
- Growing zone: USDA Plant Hardiness Zone Map, 2023. USDA Agricultural Research Service and PRISM Group, Oregon State University, prism.oregonstate.edu/phzm, accessed 8 Oct 2026.
- Then and now: NOAA’s gridded normals for 1901–2000 at the same cell.
- Storms and extremes: FEMA National Risk Index (expected annual losses to buildings).
Common questions about Islip’s climate
What is the weather like in Islip?
A typical July afternoon reaches 83°, a January night drops to 26°, and about 32 inches of snow falls in a normal winter. Milder January nights than 64% of U.S. towns; cooler July afternoons than 72% of U.S. towns.
How cold does it get in Islip in winter?
January nights average 26°. About 98 nights a year reach 32° or below. In the coldest January of the last 30 years the month averaged 25°.
How much snow does Islip get?
About 32 inches in a normal winter at Islip Li Macarthur Airport, heaviest from January through February, about 10 inches a month, with snow on the ground about 23 days a year.
How hot does it get in Islip?
July, with a typical high of 83° and a low of 67°. About 8 days a year reach 90° (Islip Li Macarthur Airport).
When is the first and last frost in Islip?
In half of years the last spring frost (32°) comes by April 10 and the first fall frost by November 2, about 207 frost-free days, at Islip Li Macarthur Airport.
What growing zone is Islip in?
Zone 7b on the 2023 USDA Plant Hardiness Zone Map: the coldest night of a typical winter reaches about 7°.
What is the best time of year to visit Islip?
By one simple rule (highs of 62–84° and lows of 40° or more), May, June, July, August, September and October. The rule is ours, not NOAA’s; the month table has the numbers to judge by.
Is Islip getting warmer?
Yes: 1991–2020 averaged 2.3° warmer than 1901–2000 on NOAA’s grid. A bigger shift than 98% of U.S. towns.
Neighbors talk weather
Gardens, snow, and the best days of the year in Islip.
Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000; USDA/PRISM 2023 hardiness zones; FEMA National Risk Index. Today’s forecast: National Weather Service.