Adelphi in Fall
In fall (September, October and November), Adelphi sees average daytime highs around 67°F and overnight lows near 50°F, with 10.6 in of precipitation over about 25 wet days across the season. It is the 2nd-warmest season and the 3rd-wettest season.
Over the season highs ease from about 83°F in early September to 52°F by late November. The sky is clear or mostly clear about 38% of the time across fall, and the air most often feels dry.
Fall is Adelphi's best season of the year to visit on our travel score. For the whole year in context, see Adelphi's year-round climate.
- Avg daytime high
- 67°F
- 2nd-warmest season
- Avg overnight low
- 50°F
- Precipitation
- 10.6 in
- 25 wet days
- Avg wind
- 6 mph
- Travel score
- 5.8
- best season of the year
- Months
- Sep · Oct · Nov
Temperature in Adelphi in Fall
Over the season highs ease from about 83°F in early September to 52°F by late November.
A typical fall day in Adelphi reaches about 67°F and drops to 50°F overnight. The warmest of the three months is September, the coolest November.
How fall really feels in Adelphi
Once humidity and wind are folded in, fall brings about 0 days that feel above 90°F and 9 that feel at or below 32°F.
The story in fall is cold — wind chill drags the overnight "feels like" below the raw low.
Adelphi weather by month
How the three fall months (September, October and November) 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 | 43° / 28° | 3.1 | 8.6 | 2.9 | 9.6 | 0.4 |
| Feb | 46° / 29° | 2.9 | 8.5 | 2.8 | 10.5 | 1.2 |
| Mar | 55° / 36° | 3.9 | 10.3 | 1.9 | 11.7 | 3.4 |
| Apr | 66° / 47° | 3.4 | 10.1 | 0.1 | 13 | 5.9 |
| May | 74° / 56° | 3.8 | 11 | 0 | 14.1 | 6.6 |
| Jun | 83° / 65° | 3.5 | 11.3 | 0 | 14.7 | 5.4 |
| Jul | 88° / 70° | 4.1 | 12.1 | 0 | 14.5 | 4.3 |
| Aug | 85° / 68° | 3.5 | 10.1 | 0 | 13.5 | 5.1 |
| Sep | 79° / 61° | 4.3 | 9.3 | 0 | 12.3 | 6.8 |
| Oct | 67° / 49° | 3.4 | 7.8 | 0 | 11 | 6.6 |
| Nov | 56° / 39° | 2.9 | 7.5 | 0.2 | 9.9 | 4.1 |
| Dec | 47° / 32° | 3.5 | 8.8 | 1.6 | 9.3 | 1.5 |
Cloud cover in Fall
The sky is clear or mostly clear about 38% of the time across fall.
Chance of precipitation in Fall
Adelphi gets around 10.6 in of rain and snow over 25 wet days across fall. The line is the day-by-day chance of measurable precipitation.
Humidity in Fall
Most of fall feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.
Wind in Fall
Winds average 6 mph across fall.
Sunrise & sunset in Fall
Daylight runs from about 12 h 54 min in early September to 9 h 30 min by late November. The lit band spans sunrise to sunset each day.
Solar energy in Fall
Average shortwave solar energy reaching the ground each day across fall, about 3.4 kWh/m².
Hazard calendar for Adelphi
In fall, Adelphi overlaps its atlantic hurricane season. The full year is below, with each hazard's peak months called out.
Adelphi sits in the Atlantic hurricane belt; the season peaks August–October.
Is fall a good time to visit Adelphi?
Our two travel scores rate fall for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal), averaged across the three months.
fall is a reasonable time to visit Adelphi for sightseeing.
What to pack for Adelphi in Fall
From fall's temperature range, rain chance, sun and wind — what's worth putting in the bag.
In fall, Adelphi sees daytime highs around 67°F and nights near 50°F. Worth packing: light clothes, a warm layer and rain gear. About 25 days see rain.
Sea temperature near Adelphi in Fall
The nearest coast averages about 64°F across fall — the other half of the beach question. The full-year curve and swim-comfort zones are below.
The sea at the nearest coast (about 33 mi away) is warmest in August at about 78°F and coldest in February near 36°F.
It's comfortable for a long swim from Jun 16 to Oct 5 — about 3.7 months when the water holds above 68°F.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°F) | 38 | 36 | 40 | 47 | 58 | 68 | 76 | 78 | 74 | 65 | 53 | 44 |
| Comfort | Bracing | Bracing | Bracing | Bracing | Bracing | Refreshing | Warm | Warm | Refreshing | Cool | Bracing | Bracing |
| Sea temperature (°F) | Comfort | |
|---|---|---|
| Jan | 38 | Bracing |
| Feb | 36 | Bracing |
| Mar | 40 | Bracing |
| Apr | 47 | Bracing |
| May | 58 | Bracing |
| Jun | 68 | Refreshing |
| Jul | 76 | Warm |
| Aug | 78 | Warm |
| Sep | 74 | Refreshing |
| Oct | 65 | Cool |
| Nov | 53 | Bracing |
| Dec | 44 | Bracing |
UV index in Adelphi in Fall
Clear-sky midday UV across fall averages around 4 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.
Under clear skies, the midday UV index in Adelphi peaks around July 10 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 19 at about 2 (low).
The index reaches 3 or more — the level where the WHO recommends sun protection — in 9 months of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 2 | 3 | 5 | 6 | 8 | 9 | 9 | 7 | 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 | 9 | Very high |
| Jul | 9 | Very high |
| Aug | 7 | High |
| Sep | 6 | High |
| Oct | 4 | Moderate |
| Nov | 3 | Moderate |
| Dec | 2 | Low |
Air quality in Adelphi in Fall
Average fine-particle pollution (PM2.5) through the year — so you can see where fall falls, not just the annual average.
Air quality in Adelphi is worst in July — around 17 µg/m³ PM2.5 (moderate), about 1.9× 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 | 12 | 13 | 13 | 15 | 16 | 17 | 15 | 12 | 9 | 9 | 10 |
| Level | Good | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Good | Good | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 11 | Good |
| Feb | 12 | Moderate |
| Mar | 13 | Moderate |
| Apr | 13 | Moderate |
| May | 15 | Moderate |
| Jun | 16 | Moderate |
| Jul | 17 | Moderate |
| Aug | 15 | Moderate |
| Sep | 12 | Moderate |
| Oct | 9 | Good |
| Nov | 9 | Good |
| Dec | 10 | Good |
Where is Adelphi?
Adelphi sits at 39.0°N, 77.0°W, 171 ft above sea level, in United States. The nearest listed city is Langley Park, 1.2 mi away.
Topography around Adelphi
How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Adelphi.
Within 2 miles, the terrain around Adelphi has only modest variations in elevation — a maximum elevation change of 358 ft around an average of 207 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 617 ft; within 50 miles, large variations in elevation — a maximum elevation change of 2,064 ft.
The land around Adelphi is covered by trees (64%) and artificial surfaces (25%) within 2 miles, trees (65%) and artificial surfaces (24%) within 10 miles, and trees (58%) 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 Adelphi (39.0032°, -76.9719°, elevation 171 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.