Williamstown in Summer
In summer (June, July and August), Williamstown sees average daytime highs around 84°F and overnight lows near 68°F, with 11.8 in of rain over about 32 wet days across the season. It is the warmest season of the year and the wettest season of the year.
Over the season highs climb from about 78°F in early June to 82°F by late August. The sky is clear or mostly clear about 28% of the time across summer, and the air most often feels muggy.
Summer is Williamstown's 2nd-best season to visit on our travel score. For the whole year in context, see Williamstown's year-round climate.
- Avg daytime high
- 84°F
- warmest season of the year
- Avg overnight low
- 68°F
- Rainfall
- 11.8 in
- 32 wet days
- Avg wind
- 6 mph
- Travel score
- 5.5
- 2nd-best season
- Months
- Jun · Jul · Aug
Temperature in Williamstown in Summer
Over the season highs climb from about 78°F in early June to 82°F by late August.
A typical summer day in Williamstown reaches about 84°F and drops to 68°F overnight. The warmest of the three months is July, the coolest June.
How summer really feels in Williamstown
Once humidity and wind are folded in, summer brings about 0 days that feel above 90°F and 0 that feel at or below 32°F.
summer sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.
Williamstown weather by month
How the three summer months (June, July and August) compare with the rest of the year — the season's months are highlighted.
| Month | High / Low (°F) | Rainfall (inches) | Wet days | Snow days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|---|
| Jan | 42° / 28° | 3.1 | 9.2 | 3.3 | 9.5 | 0.2 |
| Feb | 44° / 29° | 3.0 | 9 | 3.2 | 10.4 | 0.8 |
| Mar | 52° / 36° | 4.0 | 10.6 | 2 | 11.7 | 2.8 |
| Apr | 64° / 46° | 3.4 | 10.6 | 0.3 | 13 | 5.5 |
| May | 73° / 55° | 3.4 | 10.8 | 0 | 14.2 | 6.5 |
| Jun | 82° / 65° | 3.8 | 10.7 | 0 | 14.8 | 6.0 |
| Jul | 86° / 70° | 3.8 | 11.2 | 0 | 14.5 | 4.9 |
| Aug | 84° / 68° | 4.2 | 10.4 | 0 | 13.6 | 5.5 |
| Sep | 78° / 61° | 3.9 | 9.3 | 0 | 12.3 | 6.9 |
| Oct | 67° / 50° | 3.6 | 8 | 0 | 10.9 | 6.4 |
| Nov | 56° / 40° | 2.9 | 7.9 | 0.2 | 9.8 | 3.9 |
| Dec | 46° / 33° | 3.9 | 9.4 | 1.8 | 9.2 | 1.4 |
Cloud cover in Summer
The sky is clear or mostly clear about 28% of the time across summer.
Chance of precipitation in Summer
Williamstown gets around 11.8 in of rain over 32 wet days across summer. The line is the day-by-day chance of measurable precipitation.
Humidity in Summer
Most of summer feels muggy — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Summer
Winds average 6 mph across summer.
Sunrise & sunset in Summer
Daylight runs from about 14 h 36 min in early June to 13 hours by late August. The lit band spans sunrise to sunset each day.
Solar energy in Summer
Average shortwave solar energy reaching the ground each day across summer, about 5.8 kWh/m².
Hazard calendar for Williamstown
In summer, Williamstown overlaps its atlantic hurricane season. The full year is below, with each hazard's peak months called out.
Williamstown sits in the Atlantic hurricane belt; the season peaks August–October.
Is summer a good time to visit Williamstown?
Our two travel scores rate summer for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
summer is a reasonable time to visit Williamstown for sightseeing. The water and warmth also suit a beach or pool day.
What to pack for Williamstown in Summer
From summer's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In summer, Williamstown sees daytime highs around 84°F and nights near 68°F. Pack light clothes and sun protection. Worth having: rain gear. About 32 days see rain.
Sea temperature near Williamstown in Summer
The nearest coast averages about 72°F across summer — the other half of the beach question. The full-year curve and swim-comfort zones are below.
The sea at the nearest coast (about 39 mi away) is warmest in August at about 75°F and coldest in February near 38°F.
It's comfortable for a long swim from Jun 21 to Oct 3 — about 3.5 months when the water holds above 68°F.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°F) | 40 | 38 | 41 | 48 | 57 | 67 | 74 | 75 | 73 | 65 | 55 | 47 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Bracing | Cool | Refreshing | Warm | Refreshing | Cool | Bracing | Bracing |
| Sea temperature (°F) | Comfort | |
|---|---|---|
| Jan | 40 | Bracing |
| Feb | 38 | Bracing |
| Mar | 41 | Bracing |
| Apr | 48 | Bracing |
| May | 57 | Bracing |
| Jun | 67 | Cool |
| Jul | 74 | Refreshing |
| Aug | 75 | Warm |
| Sep | 73 | Refreshing |
| Oct | 65 | Cool |
| Nov | 55 | Bracing |
| Dec | 47 | Bracing |
UV index in Williamstown in Summer
Clear-sky midday UV across summer averages around 8 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Williamstown peaks around July 11 at about 8 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 20 at about 2 (low).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 2 | 3 | 5 | 6 | 8 | 8 | 8 | 6 | 6 | 4 | 3 | 2 |
| Level | Low | Moderate | Moderate | High | Very high | Very high | Very high | High | High | Moderate | Moderate | Low |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 2 | Low |
| Feb | 3 | Moderate |
| Mar | 5 | Moderate |
| Apr | 6 | High |
| May | 8 | Very high |
| Jun | 8 | Very high |
| Jul | 8 | Very high |
| Aug | 6 | High |
| Sep | 6 | High |
| Oct | 4 | Moderate |
| Nov | 3 | Moderate |
| Dec | 2 | Low |
Air quality in Williamstown in Summer
Average fine-particle pollution (PM2.5) through the year — so you can see where summer falls, not just the annual average.
Air quality in Williamstown is worst in July — around 18 µg/m³ PM2.5 (moderate), about 2.0× the cleanest month (November, 9 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 11 | 13 | 15 | 13 | 15 | 16 | 18 | 15 | 12 | 9 | 9 | 10 |
| Level | Good | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Good | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 11 | Good |
| Feb | 13 | Moderate |
| Mar | 15 | Moderate |
| Apr | 13 | Moderate |
| May | 15 | Moderate |
| Jun | 16 | Moderate |
| Jul | 18 | Moderate |
| Aug | 15 | Moderate |
| Sep | 12 | Good |
| Oct | 9 | Good |
| Nov | 9 | Good |
| Dec | 10 | Good |
Where is Williamstown?
Williamstown sits at 39.7°N, 75.0°W, 144 ft above sea level, in United States. The nearest listed city is Sicklerville, 2.5 mi away.
Topography around Williamstown
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Williamstown.
Within 2 miles, the terrain around Williamstown has only modest variations in elevation — a maximum elevation change of 85 ft around an average of 151 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 233 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 1,125 ft.
The land around Williamstown is covered by trees (60%) and grassland (23%) within 2 miles, trees (68%) within 10 miles, and trees (52%) and water (20%) within 50 miles.
United States travel facts
- Power plugs
- Type A / B
- 120 V · 60 Hz
- Prices
- ≈ 100% of US
- price level, 2025
- GDP per capita
- $90,027
- 2025
- Happiness
- 6.8 / 10
- World Happiness, 2025
- Safe drinking water
- 98%
- of population, 2024
- Homicide rate
- 5.8
- per 100k, 2023
- Road deaths
- 12.7
- per 100k/yr, 2019
- Income group
- High
- World Bank
- Religion
Sources: World Bank, US State Department, World Happiness Report, WHO/UNICEF, EF EPI, CIA World Factbook.
Data sources
Temperature, precipitation, cloud, humidity, wind and solar figures are a 1991–2020 climatology for Williamstown (39.6862°, -74.9952°, elevation 144 ft), computed from hourly ERA5 reanalysis — contains modified Copernicus Climate Change Service information. Sun figures are astronomical calculations, not observations. City data © GeoNames, CC BY 4.0. Map outlines from Natural Earth (public domain); interactive map © Google.