Portsmouth weather in September

In September, Portsmouth sees average daytime highs of 79°F and overnight lows near 59°F, with 3.3 in of rain across 8.1 wet days and about 12.3 hours of daylight. It is the 4th-warmest and 9th-wettest month of the year here.

Highs ease over the month, from about 83°F in the first days to 74°F by the end. The sky is clear or mostly clear about 40% 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 Portsmouth's 1st-clearest and 10th-windiest month. For the whole year in context, see Portsmouth's year-round climate.

Daytime high
79°
4th warmest
Overnight low
59°
9th coldest
Rainfall
3.3 in
8.1 wet days
Daylight
12 h 12 min
6:19 AM – 6:34 PM
Cloud cover
51%
1st clearest
Wind
5 mph
10th windiest
Solar energy
4.49 kWh/m²
Travel score
7.0
out of 10

Portsmouth is city in Scioto County, Ohio, United States.

Density
712/km²
people per km²
Founded
1803

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 83°F in the first days to 74°F by the end.

A typical September day in Portsmouth reaches about 79°F in the afternoon and slips back to 59°F overnight — a 20°F spread between the day's warmth and the night's chill. On most days the high lands between 68°F and 88°F. Set against its neighbours, September runs about 6°F cooler than August and about 12°F warmer than October.

40°60°80°151015202530
Avg high (°F)Avg low (°F)
18364
28364
38364
48263
58263
68263
78262
88162
98162
108161
118061
128060
138060
147960
157959
167959
177859
187858
197858
207757
217757
227657
237656
247656
257556
267555
277455
287454
297454
307354

How September really feels in Portsmouth

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.

Portsmouth weather by month

How September compares with the rest of the year at a glance. September is the 4th-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan41° / 27°3.410.23.69.60.1
Feb45° / 29°3.410.13.710.50.8
Mar54° / 36°4.2121.711.73.1
Apr66° / 47°4.412.40.3135.6
May74° / 56°4.612.9014.16.2
Jun82° / 64°4.313.1014.75.6
Jul85° / 68°3.912.5014.44.9
Aug85° / 66°3.011.2013.55.3
Sep79° / 59°3.38.1012.37.0
Oct67° / 48°3.190.1116.3
Nov54° / 38°3.28.70.69.93.5
Dec45° / 31°3.6102.39.30.9

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 40% of the time in September, the clearest month of the year.

Beyond those clear spells, partly cloudy skies cover about 17% of September, with mostly cloudy or overcast conditions the remaining 43%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15941
25941
35941
45941
55941
65941
75941
85941
95941
105941
115842
125743
135743
145743
155644
165644
175545
185644
195644
205545
215545
225545
235545
245743
255743
265743
275743
285842
295842
305842

Chance of precipitation in September

Any precipitation

Portsmouth gets around 3.3 in of rain over 8.1 wet days in September. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 27% and peaks near 29% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
129
229
328
428
528
627
726
826
925
1025
1125
1225
1325
1425
1525
1626
1726
1826
1927
2027
2128
2228
2328
2428
2528
2628
2728
2828
2927
3027

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 35% of days. Sticky, muggy-or-worse air turns up on roughly 20% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
11319252715
21420262614
31521262513
41621262512
51722262411
61922262310
7202326229
8222327218
9232327207
10252327196
11272327185
12282327175
13302227174
14322226164
15332226153
16352225143
17372225143
18392224132
19412224122
20432123112
21452122101
22472121101
2349212091
2451201991
2552201981
2653201881
2757191770
2858191670
2960181660
3061181560

Wind in September

Winds average 5 mph in September.

Across September, daily wind ranges from about 5 mph on the calmest days to 6 mph at its breeziest. It stays fairly steady from day to day.

0246810151015202530
Wind speed (mph)Feels
15calm
25calm
35calm
45calm
55calm
65calm
75calm
85calm
95calm
105calm
115calm
125calm
135calm
145calm
155calm
165calm
175calm
185calm
195calm
205calm
215calm
225calm
235calm
245calm
256calm
266calm
276calm
286calm
296calm
306calm

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 6:05 AM to 6:32 AM, and sunset from 6:58 PM to 6:11 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.96:056:58
212.86:066:57
312.86:076:55
412.86:086:53
512.76:096:52
612.76:106:50
712.66:116:49
812.66:126:47
912.56:126:45
1012.56:136:44
1112.56:146:42
1212.46:156:40
1312.46:166:39
1412.36:176:37
1512.36:186:35
1612.26:196:34
1712.26:206:32
1812.26:216:30
1912.16:226:29
2012.16:236:27
2112.06:236:25
2212.06:246:24
2311.96:256:22
2411.96:266:20
2511.96:276:19
2611.86:286:17
2711.86:296:16
2811.76:306:14
2911.76:316:12
3011.66:326:11

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.49 kWh/m².

For context, solar energy here swings from a low near 1.73 kWh/m² to a high of 6.11 kWh/m² in June across the year — September's 4.49 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
15.0Bright
25.0Bright
35.0Bright
44.9Bright
54.9Bright
64.9Bright
74.8Bright
84.8Bright
94.8Bright
104.7Bright
114.7Bright
124.7Bright
134.6Bright
144.6Bright
154.5Bright
164.5Bright
174.4Bright
184.4Bright
194.4Bright
204.3Bright
214.3Bright
224.2Bright
234.2Bright
244.2Bright
254.1Bright
264.1Bright
274.1Bright
284.0Bright
294.0Moderate
304.0Moderate
Planning a trip in September

Hazard calendar for Portsmouth

In seasonPeak

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

Portsmouth 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 Portsmouth?

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

7.0
Sightseeing
1st-best month of the year
6.6
Beach & pool
2nd-best month of the year

September is one of the better times to visit Portsmouth for general sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Portsmouth in September

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

In September, Portsmouth sees daytime highs around 79°F and nights near 59°F. Worth packing: light clothes and rain gear. About 8 days see rain.

light clothesrain gear

UV index in Portsmouth 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 Portsmouth peaks around June 18 at about 9 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near January 1 at about 2 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 10 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecModerateHighVery highHighModerateJun 18UV 9Jan 1UV 2
UV index (midday)Level
Jan2Low
Feb3Moderate
Mar5Moderate
Apr6High
May8Very high
Jun9Very high
Jul9Very high
Aug8Very high
Sep6High
Oct3Moderate
Nov3Moderate
Dec2Low

Air quality in Portsmouth 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 Portsmouth is worst in July — around 18 µg/m³ PM2.5 (moderate), about 2.4× the cleanest month (October, 8 µg/m³).

Modeled monthly averages (CAMS reanalysis, 2015–2024).

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1218 µg/m³Oct 248 µg/m³
PM2.5 (µg/m³)Level
Jan9Good
Feb10Good
Mar10Good
Apr11Good
May14Moderate
Jun17Moderate
Jul18Moderate
Aug15Moderate
Sep12Good
Oct8Good
Nov8Good
Dec8Good
Location & terrain

Where is Portsmouth?

Portsmouth sits at 38.7°N, 83.0°W, 531 ft above sea level, in United States. The nearest listed city is Ashland, 26 mi away.

Topography around Portsmouth

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

Within 2 miles, the terrain around Portsmouth has only modest variations in elevation — a maximum elevation change of 640 ft around an average of 620 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 817 ft; within 50 miles, significant variations in elevation — a maximum elevation change of 925 ft.

The land around Portsmouth is covered by trees (42%) within 2 miles, trees (77%) within 10 miles, and trees (77%) within 50 miles.

2 miles
640 ft
10 miles
817 ft
50 miles
925 ft
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Ashland 26 mi · Meads 27 mi · Huntington 37 mi · Chillicothe 42 mi · Athens 63 mi · Lancaster 71 mi · Charleston 78 mi · Grove City 80 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 Portsmouth (38.7317°, -82.9977°, elevation 531 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).