Williamstown has chilly winters and warm summers
A typical July afternoon reaches 87°, a January night drops to 25°, and about 22 inches of snow falls in a normal winter.
A year in Williamstown at a glance
Each month’s typical high and low, and what it brings.
What stands out about Williamstown’s climate
Read from where Williamstown sits among New Jersey’s towns. The page puts what stands out first.
Warmer than it used to be
The last 30 years in Williamstown averaged 1.9° warmer than the 1900s. The biggest change is in December (+3.4°).
A bigger shift than in 91% of U.S. towns.
Change by month
What a year in Williamstown feels like
Typical highs and lows by season and by month, from NOAA’s 30-year normals.
22 inches of snow, 47 of rain and melt
July is the wettest month and February the driest. Rain or snow falls on about 130 days a year.
Rain + melted snow by month
Inches of water
Snowfall by month
Inches of snow
About 205 frost-free days a year
In half of years the last 32° night comes by April 8 and the first by November 1.
Freezing nights by month
Average nights at or below 32°
90° days by month
Average days at 90° or more
Living with Williamstown’s climate
What the numbers mean for a garden, a driveway, a furnace and a free afternoon.
205 frost-free days. The last frost comes by Apr 8 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 1.
About 22" a winter over 6 days with an inch or more, most in February. Snow covers the ground about 21 days a year.
Months averaging under 55° run from November through April. Heating is 80% of the year’s heating-and-cooling load.
About 20 days a year reach 90°, and July afternoons average 87°.
The nicest months are April, May, June, September and October.
Parks & trails →Normals are averages. Ice storms, nor’easters, floods and heat waves are on the natural hazards page.
Natural hazards →Williamstown and its neighbors
Winslow has the coldest January nights next door (25°) and Winslow the hottest July afternoons (87°). Tap a town to see its climate.
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.
How Williamstown compares
Against every U.S. town on TownTapestry, each counted once, with its place in New Jersey.
Williamstown weather by month
Average highs, lows, rain and snow for every month, from NOAA’s 1991–2020 normals.
| Month | High | Low | Rain + melt | Snow | Wet days | Snow on ground | 30-yr range |
|---|---|---|---|---|---|---|---|
| January | 42° | 25° | 3.5" | 5.8" | 12 | 7 | 26° – 41° |
| February | 45° | 26° | 2.9" | 8.2" | 10 | 8 | 25° – 43° |
| March | 53° | 33° | 4.5" | 2.7" | 12 | 3 | 37° – 51° |
| April | 65° | 41° | 3.5" | 0.3" | 12 | 0 | 49° – 58° |
| May | 74° | 51° | 3.5" | 0 | 13 | 0 | 58° – 69° |
| June | 82° | 61° | 4.0" | 0 | 11 | 0 | 68° – 76° |
| July | 87° | 67° | 4.8" | 0 | 11 | 0 | 72° – 80° |
| August | 85° | 65° | 4.7" | 0 | 10 | 0 | 71° – 78° |
| September | 78° | 58° | 4.0" | 0 | 9 | 0 | 65° – 72° |
| October | 67° | 46° | 4.2" | 0 | 10 | 0 | 52° – 63° |
| November | 56° | 37° | 3.3" | 0.2" | 9 | 0 | 40° – 51° |
| December | 47° | 29° | 4.4" | 4.7" | 11 | 3 | 30° – 50° |
| Year | 65° | 45° | 47.1" | 21.9" | 130 | 21 |
Heating and cooling a home in Williamstown
80% of the work is heating, so the furnace matters far more than the air conditioner.
Degree days add up how far each day’s average falls below (heating) or rises above (cooling) 65° over a year. Source: NOAA station normals.
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 50°. September is the most reliable, staying within 7°.
Common questions about Williamstown’s climate
What is the coldest month in Williamstown?
January, with a typical high of 42° and a low of 25°.
What is the hottest month in Williamstown?
July, with a typical high of 87° and a low of 67°. About 20 days a year reach 90°.
How much snow does Williamstown get?
About 22 inches in a normal winter, most of it in February.
When is the first frost in Williamstown?
In half of years the first 32° night comes by November 1, and the last spring frost by April 8.
What is the rainiest month in Williamstown?
July, with 4.8 inches of rain and melted snow. The year totals 47 inches.
Neighbors talk weather
Gardens, snow, and the best days of the year in Williamstown.
Your answer becomes a post in Town Square.
Temperatures and rainfall come from NOAA’s gridded climate normals for Williamstown itself (about a 3-mile square). Snow, frost dates and day counts come from NOAA’s weather station at Somerdale 4 Sw, NJ (11 mi, snow) and Glassboro 2 Ne, NJ (8 mi, frost, heat and degree days). Normals are 30-year averages, not a forecast. Source: NOAA NCEI U.S. Climate Normals, 1991–2020 and 1901–2000. Today’s forecast: National Weather Service.