Somerville, New Jersey climate: Normal weather by month, frost dates and records
Somerville's normal year runs from 21°F January nights to 86°F July afternoons, with 45.5 inches of precipitation a year. (NOAA 1991-2020 normals)
In metric: a yearly mean of 11.4°C, January lows of −6°C, July highs of 30°C, 1,155 mm of precipitation a year.
- NOAA stationSomerville Somerset Airport
- Station IDUSW00054785
- Location40.62°N 74.67°W
- Elevation105 ft (32 m)
- From the center5 miles
- Population14,428
On October 23, the normal high in Somerville is 63°F and the normal low 39°F, and the chance of measurable rain or snow is 43%.
Normals describe a typical year at the station, not a forecast. The National Weather Service forecast for Somerville.
- Jan 39° 21°
- Feb 43° 22°
- Mar 51° 30°
- Apr 63° 39°
- May 73° 48°
- Jun 81° 58°
- Jul 86° 63°
- Aug 84° 61°
- Sep 78° 54°
- Oct 66° 42°
- Nov 55° 33°
- Dec 44° 26°
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 Somerville each month?
July is the warmest month, with normal highs of 86°F; January the coldest, with normal lows of 21°F. The most precipitation falls in August (5.18 in), the least in February (2.20 in).
| Month | High | Low | Mean | Precip. | Wet days | 90°F days | Freezing nights | Daylight |
|---|---|---|---|---|---|---|---|---|
| January | 39°F | 21°F | 29.9°F | 3.16 | 10 | <1 | 27 | 9 h 30 min |
| February | 43°F | 22°F | 32.6°F | 2.20 | 11 | <1 | 25 | 10 h 40 min |
| March | 51°F | 30°F | 40.1°F | 3.89 | 12 | <1 | 19 | 11 h 50 min |
| April | 63°F | 39°F | 51.0°F | 3.59 | 12 | <1 | 8 | 13 h 10 min |
| May | 73°F | 48°F | 60.6°F | 3.54 | 14 | 1 | 1 | 14 h 20 min |
| June | 81°F | 58°F | 69.5°F | 4.23 | 14 | 4 | <1 | 15 h |
| July | 86°F | 63°F | 74.6°F | 4.93 | 14 | 10 | <1 | 14 h 50 min |
| August | 84°F | 61°F | 72.8°F | 5.18 | 16 | 6 | <1 | 13 h 50 min |
| September | 78°F | 54°F | 65.8°F | 3.82 | 15 | 2 | <1 | 12 h 30 min |
| October | 66°F | 42°F | 54.0°F | 3.67 | 14 | <1 | 5 | 11 h 10 min |
| November | 55°F | 33°F | 43.9°F | 3.41 | 11 | <1 | 16 | 10 h |
| December | 44°F | 26°F | 35.1°F | 3.87 | 11 | <1 | 24 | 9 h 20 min |
| Year (annual) | 64°F | 41°F | 52.5°F | 45.49 | 153 | 23 | 124 |
The same normals in °C and millimetres
| Month | High | Low | Mean | Precip. |
|---|---|---|---|---|
| January | 4°C | −6°C | −1.2°C | 80 mm |
| February | 6°C | −5°C | 0.3°C | 56 mm |
| March | 10°C | −1°C | 4.5°C | 99 mm |
| April | 17°C | 4°C | 10.6°C | 91 mm |
| May | 23°C | 9°C | 15.9°C | 90 mm |
| June | 27°C | 14°C | 20.8°C | 107 mm |
| July | 30°C | 17°C | 23.7°C | 125 mm |
| August | 29°C | 16°C | 22.7°C | 132 mm |
| September | 25°C | 12°C | 18.8°C | 97 mm |
| October | 19°C | 6°C | 12.2°C | 93 mm |
| November | 13°C | 0°C | 6.6°C | 87 mm |
| December | 7°C | −3°C | 1.7°C | 98 mm |
NOAA publishes no 1991-2020 snowfall normal for this station. The nearest record that keeps one, Flemington (12 miles away), gets 27 inches of snow in a normal year; elevation and distance can change that.
Source: NOAA NCEI 1991-2020 monthly normals, station USW00054785; 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 Somerville?
Normal highs sit between 65°F and 85°F in May, June, August, September and October. Of those, June has the fewest days with rain (14).
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 USW00054785.
When is the last frost in Somerville?
In Somerville, the last spring frost (32°F) comes after April 26 in half of years and after May 13 in one year in ten; the first autumn frost comes before October 18 in half of years and before October 5 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 261 year in 10 after May 13; 9 in 10 after April 11
- First autumn frost, half of years before
- October 181 year in 10 before October 5; 9 in 10 before November 2
NOAA puts the median frost-free season at 176 days, and the season without a hard freeze (28°F) at 202 days.
A hard freeze (28°F) comes after April 11 in half of springs and before October 30 in half of autumns.
The USDA's 2023 Plant Hardiness Zone Map puts Somerville in zone 7a in ZIP code 08876. By the map's own method, the average of each year's coldest night over 1991-2020, Somerville's NOAA station is in zone 6b: the coldest night of a typical year reaches 0°F (16 complete years); the map interpolates between stations and terrain, so the station and the ZIP area can differ by half a zone.
Frost dates for every NOAA station in New Jersey · Frost dates by ZIP code
Source: NOAA NCEI 1991-2020 annual normals (frost probabilities), station USW00054785; 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 Somerville?
In a normal year in Somerville, 23 days a year reach 90°F (1 of them 100°F or more), 124 nights fall to 32°F or colder and 153 days bring measurable precipitation.
- Days at 90°F or more
- 23a normal year
- Days at 100°F or more
- 1a normal year
- Nights at 32°F or colder
- 124a normal year
- Days that stay below freezing
- 17high of 32°F or less
- Days with 0.01 inch of precipitation
- 153a normal year
Source: NOAA NCEI 1991-2020 annual normals, station USW00054785.
How sunny is Somerville?
Over a year 73% of the sunlight that would reach the ground under clear skies gets through the clouds in the area around Somerville, 3.9 kWh per square metre a day. July is the sunniest month (80%) and December the cloudiest (66%).
| Month | Share of clear-sky sunshine | Sunshine, kWh/m² a day |
|---|---|---|
| January | 68% | 1.9 |
| February | 71% | 2.8 |
| March | 69% | 3.7 |
| April | 71% | 4.8 |
| May | 70% | 5.4 |
| June | 76% | 6.0 |
| July | 80% | 6.0 |
| August | 78% | 5.2 |
| September | 76% | 4.3 |
| October | 71% | 3.0 |
| November | 72% | 2.2 |
| 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 Somerville need?
A normal year in Somerville brings 5,385 heating degree days, 0% more than the median U.S. place (5,373), and 859 cooling degree days, 5% 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 3,215 growing degree days a year above 50°F.
| Month | Heating | Cooling |
|---|---|---|
| January | 1,086 | 0 |
| February | 909 | 0 |
| March | 772 | 0 |
| April | 427 | 7 |
| May | 178 | 41 |
| June | 28 | 163 |
| July | 1 | 299 |
| August | 4 | 246 |
| September | 71 | 94 |
| October | 352 | 11 |
| November | 633 | 0 |
| December | 925 | 0 |
| Year (annual) | 5,385 | 859 |
Source: NOAA NCEI 1991-2020 monthly normals, station USW00054785. 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 Somerville been warmer than normal lately?
2024 averaged 55.1°F, 2.6°F above the 1991-2020 normal of 52.5°F. 4 of the 4 complete years since 2021 ran warmer than the normal.
| Year | Mean | Against normal | Precip. |
|---|---|---|---|
| 2021 | 54.1°F | +1.6°F | 48.99 |
| 2022 | 53.5°F | +1.0°F | 40.94 |
| 2023 | 54.6°F | +2.1°F | 47.81 |
| 2024 | 55.1°F | +2.6°F | 44.64 |
Source: observed years: ACIS, station USW00054785. A year counts only with all twelve months complete.
How does Somerville's climate compare?
Somerville is warmer than 8 of the other 32 places with their own NOAA record in New Jersey, and wetter than 4. Across the 7,247 U.S. stations with normals, its annual mean of 52.5°F is warmer than 52%.
In the Köppen classification computed from these normals, Somerville 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 Somerville share this climate record?
25 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.
- Bradley Gardens, NJ14,315 people · 4 mi S
- Martinsville, NJ12,016 people · 5 mi E
- Manville, NJ11,031 people · 7 mi SE
- The Hills, NJ10,732 people · 3 mi NE
- Raritan, NJ8,584 people · 4 mi S
- Bernardsville, NJ8,020 people · 8 mi NE
- Basking Ridge, NJ7,882 people · 8 mi NE
- Green Knoll, NJ6,664 people · 3 mi SE
- Bridgewater Center, NJ6,198 people · 2 mi SE
- Finderne, NJ5,968 people · 7 mi SE
- Lyons, NJ5,444 people · 7 mi NE
- Mendham, NJ5,000 people · 11 mi N
- White House Station, NJ3,758 people · 5 mi W
- Peapack and Gladstone, NJ2,602 people · 6 mi N
- Weston, NJ2,111 people · 9 mi SE
- Long Valley, NJ2,107 people · 12 mi NW
- Liberty Corner, NJ1,789 people · 5 mi NE
- Chester, NJ1,695 people · 12 mi N
- Bedminster, NJ1,463 people · 4 mi N
- Far Hills, NJ935 people · 5 mi NE
- Pluckemin, NJ490 people · 2 mi NE
- Oldwick, NJ446 people · 5 mi NW
- Pottersville, NJ314 people · 7 mi NW
- Lamington, NJ218 people · 4 mi NW
- Zarephath, NJ38 people · 8 mi SE
Source: Census Bureau 2024 Gazetteer (place centers) and Vintage 2024 population estimates. Distance and direction from the station to each place's center.
What do Somerville's other NOAA stations record?
One more NOAA station keeps 1991-2020 normals in or near Somerville. This page uses Somerville Somerset Airport; the other differs by site and elevation:
| Station | From the center | Elevation | Year | Jan low | Jul high | Precip. | Snow | Last frost |
|---|---|---|---|---|---|---|---|---|
| Somerville (4 mi NW) USC00288194 | 4 mi NW | 134 ft | 51.1°F | 19°F | 86°F | 46.7 | – | April 30 |
Source: NOAA NCEI 1991-2020 normals for each station. Last frost: the median last spring date of 32°F.
Questions about Somerville's climate
What is the coldest month in Somerville?
January, with a normal high of 39°F and a normal low of 21°F. The warmest is July (86°F by day, 63°F at night).
Does it snow in Somerville?
Yes. NOAA publishes no 1991-2020 snowfall normal for Somerville's NOAA station; the nearest record that keeps one, Flemington (12 miles away), records 27 inches of snow in a normal year.
What is the rainiest month in Somerville?
August, with 5.18 in of precipitation in a normal year; the driest is February with 2.20 in.
What plant hardiness zone is Somerville in?
The USDA's 2023 map puts Somerville in zone 7a in ZIP code 08876. By the same method at Somerville's NOAA station, the coldest night of a typical year reaches 0°F (16 years, 1991-2020): zone 6b.
How late can frost come in Somerville?
In half of years the last 32°F night comes after April 26; in one year in ten it comes after May 13. Waiting until May 13 leaves about a one-in-ten chance of a later frost.
Nearby and next
- New Jersey climateThe statewide normals and every place in the state
- Flemington, NJ12 miles from this station, 52.1°F a year
- Wertsville (4 mi NE), NJ13 miles from this station, 52.5°F a year
- Plainfield, NJ14 miles from this station, 54.9°F a year
- New Brunswick, NJ17 miles from this station, 53.7°F a year
- Compare two placesMonth by month, side by side
Download these normals (CSV) · JSON · How these figures are made