Philadelphia weather in September

In September, Philadelphia sees average daytime highs of 78°F and overnight lows near 61°F, with 4.1 in of rain across 9.2 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 1st-wettest month of the year here.

Highs ease over the month, from about 82°F in the first days to 73°F by the end. The sky is clear or mostly clear about 36% of the time in September, and the air most often feels dry.

Daylight stretches from about 12 h 54 min at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is Philadelphia's 2nd-clearest and 9th-windiest month. For the whole year in context, see Philadelphia's year-round climate.

Daytime high
78°
4th warmest
Overnight low
61°
9th coldest
Rainfall
4.1 in
9.2 wet days
Daylight
12 h 18 min
5:47 AM – 6:03 PM
Cloud cover
55%
2nd clearest
Wind
6 mph
9th windiest
Solar energy
4.23 kWh/m²
Travel score
6.9
out of 10

Philadelphia is largest city in the U.S. state of Pennsylvania and seat of Philadelphia County.

Density
4,258/km²
people per km²
Founded
1682

Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 82°F in the first days to 73°F by the end.

A typical September day in Philadelphia reaches about 78°F in the afternoon and slips back to 61°F overnight — a 17°F spread between the day's warmth and the night's chill. On most days the high lands between 69°F and 86°F. Set against its neighbours, September runs about 7°F cooler than August and about 12°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
18265
28265
38265
48165
58164
68164
78064
88064
98063
108063
117962
127962
137862
147861
157861
167761
177760
187760
197660
207659
217659
227558
237558
247458
257457
267457
277357
287356
297356
307255

How September really feels in Philadelphia

Once humidity and wind are folded in, September averages 0 days that feel above 90°F and 0 that feel at or below 32°F — the comfort signal a plain temperature reading hides.

Days feeling ≥ 90°F
0
heat index over the day's high
Days feeling ≤ 32°F
0
wind chill below the day's low

September sits comfortably in between — no days that feel dangerously hot or drop to a hard freeze once humidity and wind are folded in.

Philadelphia weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 1st-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan40° / 27°3.29.33.89.50.0
Feb43° / 28°3.08.93.410.40.6
Mar52° / 35°4.110.52.611.72.7
Apr64° / 46°3.610.20.3135.5
May73° / 55°3.511.1014.26.5
Jun82° / 64°3.810.7014.85.9
Jul86° / 70°3.910.7014.54.8
Aug84° / 68°3.710.3013.65.5
Sep78° / 61°4.19.2012.36.9
Oct66° / 49°3.68.2010.96.3
Nov55° / 39°2.97.80.39.83.6
Dec45° / 32°3.99.31.99.21.1

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 36% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 16% of September, with mostly cloudy or overcast conditions the remaining 48%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15347
25446
35347
45347
55446
65446
75446
85446
95446
105446
115446
125446
135446
145446
155347
165347
175149
185050
195050
205050
215050
225050
234951
244951
254951
265050
275050
285149
295149
305248

Chance of precipitation in September

Any precipitation

Philadelphia gets around 4.1 in of rain over 9.2 wet days in September, the wettest month. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 30% and peaks near 32% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
127
227
328
428
528
628
728
829
929
1029
1129
1229
1329
1429
1529
1629
1729
1830
1930
2031
2131
2231
2332
2432
2532
2632
2732
2832
2931
3031

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

Most of September feels dry — the stacked bands show each day's mix of comfort levels, read off the dew point.

By dew point, September lands in the dry band about 37% of days. Sticky, muggy-or-worse air turns up on roughly 22% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
12021222313
22121222313
32221222213
42321212113
52422212112
62522212012
72622211911
82722211911
92922211810
103022221710
11312222179
12322122168
13342122168
14352122157
15362122156
16372122146
17392122145
18402122134
19412121134
20422121134
21432120123
22442119123
23462119122
24472118122
25482117122
26502116112
27512116111
28532015111
29532015111
30551914111

Wind in September

Winds average 6 mph in September.

Across September, daily wind ranges from about 6 mph on the calmest days to 7 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
16calm
26calm
36calm
46calm
56calm
66calm
76calm
86calm
96calm
106calm
116calm
126calm
136calm
146calm
156calm
166calm
176calm
186calm
196calm
206calm
216calm
226calm
236calm
246calm
256calm
266calm
276calm
287calm
297calm
307calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 54 min at the start of September to 11 h 36 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 78 minutes over September. Sunrise moves from 5:33 AM to 6:01 AM, and sunset from 6:28 PM to 5:39 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.95:336:28
212.95:346:26
312.85:356:25
412.85:366:23
512.75:376:21
612.75:376:20
712.75:386:18
812.65:396:16
912.65:406:15
1012.55:416:13
1112.55:426:11
1212.45:436:10
1312.45:446:08
1412.35:456:06
1512.35:466:04
1612.35:476:03
1712.25:486:01
1812.25:495:59
1912.15:505:58
2012.15:515:56
2112.05:525:54
2212.05:535:52
2311.95:545:51
2411.95:555:49
2511.95:565:47
2611.85:575:46
2711.85:585:44
2811.75:595:42
2911.76:005:41
3011.66:015:39

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.23 kWh/m².

For context, solar energy here swings from a low near 1.82 kWh/m² to a high of 6.03 kWh/m² in June across the year — September's 4.23 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.8Bright
24.8Bright
34.7Bright
44.7Bright
54.7Bright
64.6Bright
74.6Bright
84.5Bright
94.5Bright
104.5Bright
114.4Bright
124.4Bright
134.3Bright
144.3Bright
154.3Bright
164.2Bright
174.2Bright
184.2Bright
194.1Bright
204.1Bright
214.0Bright
224.0Bright
234.0Moderate
243.9Moderate
253.9Moderate
263.8Moderate
273.8Moderate
283.8Moderate
293.7Moderate
303.7Moderate
Planning a trip in September

Hazard calendar for Philadelphia

In seasonPeak

In September, Philadelphia sits inside its atlantic hurricane season. The full year is below, with each hazard's peak months called out.

Philadelphia sits in the Atlantic hurricane belt; the season peaks August–October.

Atlantic hurricane
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Philadelphia?

Our two travel scores rate September for general sightseeing and for beach or pool weather — 0 (poor) to 10 (ideal).

6.9
Sightseeing
1st-best month of the year
6.3
Beach & pool
4th-best month of the year

September is a reasonable time to visit Philadelphia for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Philadelphia in September

From September's temperature range, rain chance, sun and wind — what's worth putting in the bag.

In September, Philadelphia sees daytime highs around 78°F and nights near 61°F. Worth packing: light clothes and rain gear. About 9 days see rain.

light clothesrain gear

UV index in Philadelphia in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 6 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Philadelphia peaks around July 10 at about 8 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 21 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 8 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateLowJul 10UV 8Dec 21UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May8Very high
Jun8Very high
Jul8Very high
Aug6High
Sep6High
Oct3Moderate
Nov3Moderate
Dec2Low

Air quality in Philadelphia in September

GoodModeratePoorUnhealthyVery unhealthy

Average fine-particle pollution (PM2.5) through the year — so you can see where September falls, not just the annual average.

Air quality in Philadelphia 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).

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1317 µg/m³Nov 129 µg/m³
PM2.5 (µg/m³)Level
Jan11Good
Feb13Moderate
Mar15Moderate
Apr13Moderate
May15Moderate
Jun16Moderate
Jul18Moderate
Aug15Moderate
Sep12Good
Oct9Good
Nov9Good
Dec10Good
Location & terrain

Where is Philadelphia?

Philadelphia sits at 40.0°N, 75.2°W, 39 ft above sea level, in United States. The nearest listed city is Center City, 0.0 mi away.

Topography around Philadelphia

How much the land rises and falls, and what covers it, within 2, 10 and 50 miles of Philadelphia.

Within 2 miles, the terrain around Philadelphia has only modest variations in elevation — a maximum elevation change of 200 ft around an average of 49 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 489 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 1,516 ft.

The land around Philadelphia is covered by artificial surfaces (81%) within 2 miles, trees (42%) and artificial surfaces (40%) within 10 miles, and trees (64%) within 50 miles.

2 miles
200 ft
10 miles
489 ft
50 miles
1,516 ft
treesgrasslandcroplandartificial surfaceswaterwetland
September weather nearby: Center City 0.0 mi · Rittenhouse 0.6 mi · Point Breeze 1.2 mi · University City 1.9 mi · Fishtown 1.9 mi · Wharton 1.9 mi · Pennsport 1.9 mi · Lower Moyamensing 2.5 mi

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
Protestant 47%unaffiliated 23%Roman Catholic 21%Jewish 2%

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 Philadelphia (39.9524°, -75.1636°, elevation 39 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. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Monthly air-quality (PM2.5) seasonality is from the CAMS EAC4 reanalysis (Copernicus Atmosphere Monitoring Service), scaled to the WHO annual mean where available. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).