Photo: Iracaz · CC BY-SA 3.0The climate in Stony Brook sits close to the middle of U.S. towns
High summer brings afternoon highs near 83°. Its July afternoons stay fresher than in 71% of U.S. towns. The latest 30-year average runs 2.3° warmer than 1901–2000’s, with December up the most. Seedlings are safe outdoors from about April 15, with the first autumn frost due around November 10.
A year in Stony Brook at a glance
Each month’s typical high and low, and what it brings.
What stands out about Stony Brook’s climate
Compared with towns across the U.S., with Stony Brook’s place in New York beside it.
What a year in Stony Brook feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
About 208 frost-free days a year
In half of years the last 32° night comes by April 15 and the first by November 10. Frost and day counts come from NOAA’s station at Setauket Strong, NY, 4 miles from the town’s center, at about the same height.
The 2023 USDA map puts Stony Brook’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 46 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 Stony Brook
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 Setauket Strong, NY.
Living with Stony Brook’s climate
What the numbers mean for a garden, a free afternoon and a bad-weather day.
208 frost-free days in zone 7b. The last frost comes by Apr 15 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 10.
Months with highs of 62–84° and lows of 40° or more: May, June, July, August, September and October. 7.4 miles of trails are waiting.
Parks & trails →Of the yearly building losses FEMA expects in Stony Brook from natural hazards, river flooding is the largest share (60%); heat waves, cold waves, winter storms and ice storms together are 7%. Normals are averages; the hazards page covers the extremes.
Natural hazards →Stony Brook and its neighbors
Brookhaven has the coldest January nights next door (23°, 2° 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 Stony Brook’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 |
|---|---|---|---|---|
| Stony Brook, NY | 25° | 83° | 46" | 32" |
| Uniontown, PA | 22° | 84° | 45" | 28" |
| Manchester, MD | 22° | 84° | 47" | 34" |
| Bridgeport, WV | 23° | 84° | 47" | 24" |
| Blacksburg, VA | 25° | 84° | 43" | 25" |
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 Stony Brook 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.
How Stony Brook compares
Against 12,954 U.S. towns of 2,500 or more (one per 5 km climate cell), with Stony Brook’s place among New York’s.
Stony Brook weather by month
Highs, lows and precipitation from NOAA’s grid at Stony Brook’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° | 25° | 3.5" | 10.3" | 11 | 7 | 24° – 38° |
| February | 41° | 25° | 3.1" | 9.4" | 10 | 9 | 21° – 39° |
| March | 48° | 32° | 4.4" | 6.5" | 11 | 4 | 35° – 48° |
| April | 59° | 41° | 4.1" | 0.6" | 11 | 0 | 46° – 54° |
| May | 68° | 50° | 3.6" | 0.0" | 12 | 0 | 55° – 63° |
| June | 78° | 60° | 4.0" | 0.0" | 10 | 0 | 65° – 72° |
| July | 83° | 67° | 3.5" | 0.0" | 9 | 0 | 70° – 78° |
| August | 82° | 65° | 3.8" | 0.0" | 9 | 0 | 69° – 77° |
| September | 75° | 59° | 4.0" | 0.0" | 9 | 0 | 64° – 71° |
| October | 65° | 48° | 4.3" | 0.0" | 9 | 0 | 52° – 62° |
| November | 54° | 38° | 3.5" | 0.5" | 10 | 0 | 41° – 50° |
| December | 45° | 30° | 4.5" | 4.5" | 12 | 3 | 30° – 49° |
| Year | 61° | 45° | 46.3" | 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 30° to 49°. June is the most reliable, staying within 7°.
Where Stony Brook’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 Stony Brook’s center.
- Snow: Islip Li Macarthur Airport.
- Frost, freezing nights, 90° and 100° days, heating and cooling: Setauket Strong, NY, 4 miles from the town’s center, at about the same height; the nearest station that passes our checks for distance, height and agreement with the grid.
- 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 Stony Brook’s climate
What is the weather like in Stony Brook?
A typical July afternoon reaches 83°, a January night drops to 25°, and about 32 inches of snow falls in a normal winter. Milder January nights than 61% of U.S. towns; cooler July afternoons than 71% of U.S. towns.
How cold does it get in Stony Brook in winter?
January nights average 25°. About 96 nights a year reach 32° or below. In the coldest January of the last 30 years the month averaged 24°.
How much snow does Stony Brook 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 Stony Brook?
July, with a typical high of 83° and a low of 67°. About 17 days a year reach 90° (Setauket Strong, NY).
When is the first and last frost in Stony Brook?
In half of years the last spring frost (32°) comes by April 15 and the first fall frost by November 10, about 208 frost-free days, at Setauket Strong, NY.
What growing zone is Stony Brook 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 Stony Brook?
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 Stony Brook 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 Stony Brook.
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.