South Portland weather in September

In September, South Portland sees average daytime highs of 65°F and overnight lows near 57°F, with 3.7 in of rain across 8.7 wet days and about 12.3 hours of daylight. It is the 3rd-warmest and 9th-wettest month of the year here.

Highs ease over the month, from about 68°F in the first days to 62°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 13 h 06 min at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is South Portland's 1st-clearest and 9th-windiest month. For the whole year in context, see South Portland's year-round climate.

Daytime high
65°
3rd warmest
Overnight low
57°
10th coldest
Rainfall
3.7 in
8.7 wet days
Daylight
12 h 18 min
5:26 AM – 5:44 PM
Cloud cover
53%
1st clearest
Wind
9 mph
9th windiest
Solar energy
4.19 kWh/m²
Travel score
6.2
out of 10

South Portland is city in Cumberland County, Maine, United States.

Density
704/km²
people per km²
Founded
1895

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 68°F in the first days to 62°F by the end.

A typical September day in South Portland reaches about 65°F in the afternoon and slips back to 57°F overnight — a 8°F spread between the day's warmth and the night's chill. On most days the high lands between 60°F and 71°F. Set against its neighbours, September runs about 6°F cooler than August and about 9°F warmer than October.

40°50°60°70°80°151015202530
Avg high (°F)Avg low (°F)
16961
26960
36960
46860
56860
66860
76759
86759
96759
106758
116658
126658
136658
146657
156557
166557
176556
186556
196456
206456
216455
226455
236355
246355
256354
266254
276253
286253
296153
306153

How September really feels in South Portland

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.

South Portland weather by month

How September compares with the rest of the year at a glance. September is the 3rd-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°F)Rainfall (inches)Wet daysSnow daysDaylight (hours)Travel score
Jan32° / 20°3.99.96.99.10.0
Feb33° / 21°3.68.96.510.20.0
Mar38° / 28°4.610.95.611.60.0
Apr47° / 38°4.710.71.913.21.6
May56° / 47°3.9110.114.53.7
Jun65° / 56°4.010.3015.25.7
Jul71° / 63°3.19.2014.96.7
Aug71° / 63°3.28.4013.86.9
Sep65° / 57°3.78.7012.36.2
Oct56° / 47°5.410.60.210.83.8
Nov46° / 37°4.510.41.49.51.3
Dec37° / 28°4.9115.88.80.0

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 15% of September, with mostly cloudy or overcast conditions the remaining 45%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16040
25842
35842
45743
55743
65743
75644
85644
95644
105644
115545
125545
135545
145545
155545
165545
175446
185545
195446
205446
215446
225347
235347
245347
255248
265248
275248
285248
295248
305248

Chance of precipitation in September

Any precipitation

South Portland gets around 3.7 in of rain over 8.7 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 29% and peaks near 31% on the wettest days.

0%10%20%30%40%151015202530
Rain chance (%)
126
226
327
428
528
629
729
830
930
1030
1130
1230
1330
1430
1530
1630
1729
1829
1929
2029
2129
2229
2329
2429
2529
2629
2730
2830
2930
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 51% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
12736298
22936288
33135268
43235257
53435247
63535237
73734226
83834226
94034215
104133215
114332204
124432204
134631193
144831193
154930182
165130172
175229172
185429161
195628151
205827141
215827141
226026131
236225121
246424111
256623101
26682291
27702181
28732070
29751960
30761860

Wind in September

Winds average 9 mph in September.

Across September, daily wind ranges from about 8 mph on the calmest days to 9 mph at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (mph)Feels
18light breeze
28light breeze
38light breeze
48light breeze
58light breeze
68light breeze
78light breeze
88light breeze
98light breeze
108light breeze
118light breeze
129light breeze
139light breeze
149light breeze
159light breeze
169light breeze
179light breeze
189light breeze
199light breeze
209light breeze
219light breeze
229light breeze
239light breeze
249light breeze
259light breeze
269light breeze
279light breeze
289light breeze
299light breeze
309light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 06 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 90 minutes over September. Sunrise moves from 5:09 AM to 5:43 AM, and sunset from 6:12 PM to 5:18 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.15:096:12
213.05:106:10
313.05:116:09
412.95:136:07
512.95:146:05
612.85:156:03
712.85:166:01
812.75:175:59
912.75:185:57
1012.65:195:56
1112.55:215:54
1212.55:225:52
1312.45:235:50
1412.45:245:48
1512.35:255:46
1612.35:265:44
1712.25:285:42
1812.25:295:40
1912.15:305:38
2012.15:315:36
2112.05:325:35
2212.05:335:33
2311.95:355:31
2411.95:365:29
2511.85:375:27
2611.85:385:25
2711.75:395:23
2811.75:415:21
2911.65:425:19
3011.65:435:18

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.19 kWh/m².

For context, solar energy here swings from a low near 1.46 kWh/m² to a high of 6.02 kWh/m² in July across the year — September's 4.19 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.9Bright
24.9Bright
34.8Bright
44.8Bright
54.7Bright
64.7Bright
74.6Bright
84.6Bright
94.5Bright
104.5Bright
114.4Bright
124.4Bright
134.3Bright
144.3Bright
154.2Bright
164.2Bright
174.1Bright
184.1Bright
194.0Bright
204.0Bright
214.0Moderate
223.9Moderate
233.8Moderate
243.8Moderate
253.7Moderate
263.7Moderate
273.6Moderate
283.6Moderate
293.5Moderate
303.5Moderate
Planning a trip in September

Hazard calendar for South Portland

In seasonPeak

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

South Portland 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 South Portland?

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

6.2
Sightseeing
3rd-best month of the year
2.4
Beach & pool
3rd-best month of the year

September is a reasonable time to visit South Portland for sightseeing.

What to pack for South Portland in September

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

In September, South Portland sees daytime highs around 65°F and nights near 57°F. Worth packing: rain gear. About 9 days see rain.

rain gear

Sea temperature near South Portland in September

The nearest coast averages about 60°F in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea offshore is warmest in August at about 63°F and coldest in March near 38°F.

The water stays below 68°F all year — cool enough that most swimmers want a wetsuit.

40°50°60°70°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshing
Sea temperature (°F)Comfort
Jan42Bracing
Feb39Bracing
Mar38Bracing
Apr42Bracing
May48Bracing
Jun55Bracing
Jul62Cool
Aug63Cool
Sep60Cool
Oct54Bracing
Nov49Bracing
Dec45Bracing

UV index in South Portland 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 South Portland peaks around July 12 at about 7 (very high) — sunscreen and a hat are worth it in the middle of the day. It bottoms out near December 23 at about 1 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 7 months of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighModerateModerateLowJul 12UV 7Dec 23UV 1
UV index (midday)Level
Jan1Low
Feb2Moderate
Mar4Moderate
Apr5Moderate
May7High
Jun7High
Jul7Very high
Aug4Moderate
Sep6High
Oct3Moderate
Nov2Low
Dec1Low
Location & terrain

Where is South Portland?

South Portland sits at 43.6°N, 70.2°W, 23 ft above sea level, in United States. The nearest listed city is Portland, 1.2 mi away.

Topography around South Portland

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

Within 2 miles, the terrain around South Portland has only modest variations in elevation — a maximum elevation change of 207 ft around an average of 46 ft above sea level; within 10 miles, only modest variations in elevation — a maximum elevation change of 548 ft; within 50 miles, large variations in elevation — a maximum elevation change of 2,182 ft.

The land around South Portland is covered by water (36%), trees (32%) and artificial surfaces (22%) within 2 miles, water (48%) and trees (37%) within 10 miles, and trees (60%) and water (34%) within 50 miles.

2 miles
207 ft
10 miles
548 ft
50 miles
2,182 ft
treesgrasslandcroplandartificial surfaceswaterwetland
September weather nearby: Portland 1.2 mi · South Portland Gardens 3.7 mi · Westbrook 6.8 mi · West Scarborough 8.7 mi · Saco 14 mi · Biddeford 15 mi · Brunswick 24 mi · Sanford 30 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 South Portland (43.6415°, -70.2409°, elevation 23 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). Sea temperatures are the NOAA OISST v2.1 1991–2020 monthly climatology (public domain), sampled at the nearest ocean point. UV index is derived from CAMS (Copernicus Atmosphere Monitoring Service) clear-sky UV data — contains modified Copernicus Atmosphere Monitoring Service information. Topography is sampled from the Copernicus DEM GLO-90 elevation model (© ESA/Airbus) and ESA WorldCover 2021 land cover (CC BY 4.0).