Porsgrunn weather in September

In September, Porsgrunn sees average daytime highs of 15°C and overnight lows near 8°C, with 101 mm of rain across 11.5 wet days and about 12.6 hours of daylight. It is the 4th-warmest and 4th-wettest month of the year here.

Highs ease over the month, from about 17°C in the first days to 13°C by the end. The sky is clear or mostly clear about 25% of the time in September, and the air most often feels dry.

Daylight stretches from about 13 h 54 min at the start of September to 11 h 18 min by month's end. Set against the rest of the year, September is Porsgrunn's 7th-clearest and 6th-windiest month. For the whole year in context, see Porsgrunn's year-round climate.

Daytime high: 15°; 4th warmest
Overnight low: 8°; 9th coldest
Rainfall: 101 mm; 11.5 wet days
Daylight: 12 h 30 min; 6:00 AM – 6:31 PM
Cloud cover: 64%; 7th clearest
Wind: 11 km/h; 6th windiest
Solar energy: 2.59 kWh/m²
Travel score: 4.4; out of 10

Porsgrunn is town in Porsgrunn Municipality, Norway.

Air quality: Good; PM2.5 7.4 µg/m³ · 2019
Founded: 1807

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

← August Porsgrunn year-round climate October →Best places to visit in September

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

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Highs ease over the month, from about 17°C in the first days to 13°C by the end.

A typical September day in Porsgrunn reaches about 15°C in the afternoon and slips back to 8°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 12°C and 19°C. Set against its neighbours, September runs about 4°C cooler than August and about 6°C warmer than October.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Avg high (°C)	18	17	17	17	17	17	17	17	16	16	16	16	16	16	15	15	15	15	15	15	14	14	14	14	14	14	13	13	13	13
Avg low (°C)	10	10	10	10	10	9	9	9	9	9	9	9	9	8	8	8	8	8	8	8	8	7	7	7	7	7	7	7	6	6

	Avg high (°C)	Avg low (°C)
1	18	10
2	17	10
3	17	10
4	17	10
5	17	10
6	17	9
7	17	9
8	17	9
9	16	9
10	16	9
11	16	9
12	16	9
13	16	9
14	16	8
15	15	8
16	15	8
17	15	8
18	15	8
19	15	8
20	15	8
21	14	8
22	14	7
23	14	7
24	14	7
25	14	7
26	14	7
27	13	7
28	13	7
29	13	6
30	13	6

How September really feels in Porsgrunn

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

Days feeling ≥ 32°C

heat index over the day's high

Days feeling ≤ 0°C

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.

Porsgrunn weather by month

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

Month	High / Low (°C)	Rainfall (mm)	Wet days	Snow days	Daylight (hours)	Travel score
Jan	0° / -5°	92	12.2	10.3	6.6	0.0
Feb	1° / -5°	62	9.3	8.4	8.8	0.0
Mar	5° / -3°	63	8.7	6.6	11.3	0.2
Apr	10° / 1°	59	9.4	3.5	14.1	2.1
May	15° / 6°	74	10.8	0.6	16.6	4.3
Jun	18° / 10°	94	12.5	0	18	5.5
Jul	20° / 12°	99	12.5	0	17.4	5.9
Aug	20° / 12°	106	13.4	0	15.2	5.7
Sep	15° / 8°	101	11.5	0	12.6	4.4
Oct	10° / 4°	107	12.5	1.5	9.8	1.9
Nov	5° / 0°	108	13	5.3	7.4	0.1
Dec	1° / -3°	84	12.2	8	5.9	0.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 25% 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 59%.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Clearer (%)	41	40	40	41	41	41	41	41	41	41	42	42	42	42	42	42	42	42	42	42	42	41	41	41	41	41	39	39	39	39
Cloudier (%)	59	60	60	59	59	59	59	59	59	59	58	58	58	58	58	58	58	58	58	58	58	59	59	59	59	59	61	61	61	61

	Clearer (%)	Cloudier (%)
1	41	59
2	40	60
3	40	60
4	41	59
5	41	59
6	41	59
7	41	59
8	41	59
9	41	59
10	41	59
11	42	58
12	42	58
13	42	58
14	42	58
15	42	58
16	42	58
17	42	58
18	42	58
19	42	58
20	42	58
21	42	58
22	41	59
23	41	59
24	41	59
25	41	59
26	41	59
27	39	61
28	39	61
29	39	61
30	39	61

Chance of precipitation in September

Any precipitation

Porsgrunn gets around 101 mm of rain over 11.5 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 39% and peaks near 42% on the wettest days.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Rain chance (%)	42	41	41	41	41	41	41	41	41	41	41	41	41	40	40	39	39	38	37	37	36	36	36	36	36	36	37	37	38	38

	Rain chance (%)
1	42
2	41
3	41
4	41
5	41
6	41
7	41
8	41
9	41
10	41
11	41
12	41
13	41
14	40
15	40
16	39
17	39
18	38
19	37
20	37
21	36
22	36
23	36
24	36
25	36
26	36
27	37
28	37
29	38
30	38

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 94% of days. It rarely turns muggy — the humid and sticky bands barely register.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Dry (%)	86	87	88	89	91	91	92	92	93	93	93	94	94	95	95	96	96	96	96	97	97	97	97	97	98	98	98	98	98	98
Comfortable (%)	13	12	11	10	9	9	8	8	7	7	7	6	6	5	5	4	4	4	4	3	3	3	3	3	2	2	2	2	2	2
Humid (%)	1	1	1	1	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0

	Dry (%)	Comfortable (%)	Humid (%)
1	86	13	1
2	87	12	1
3	88	11	1
4	89	10	1
5	91	9	0
6	91	9	0
7	92	8	0
8	92	8	0
9	93	7	0
10	93	7	0
11	93	7	0
12	94	6	0
13	94	6	0
14	95	5	0
15	95	5	0
16	96	4	0
17	96	4	0
18	96	4	0
19	96	4	0
20	97	3	0
21	97	3	0
22	97	3	0
23	97	3	0
24	97	3	0
25	98	2	0
26	98	2	0
27	98	2	0
28	98	2	0
29	98	2	0
30	98	2	0

Wind in September

Winds average 11 km/h in September.

Across September, daily wind ranges from about 10 km/h on the calmest days to 11 km/h at its breeziest. It stays fairly steady from day to day.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Wind speed (km/h)	10	10	10	10	10	10	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11	11
Feels	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm	calm

	Wind speed (km/h)	Feels
1	10	calm
2	10	calm
3	10	calm
4	10	calm
5	10	calm
6	10	calm
7	11	calm
8	11	calm
9	11	calm
10	11	calm
11	11	calm
12	11	calm
13	11	calm
14	11	calm
15	11	calm
16	11	calm
17	11	calm
18	11	calm
19	11	calm
20	11	calm
21	11	calm
22	11	calm
23	11	calm
24	11	calm
25	11	calm
26	11	calm
27	11	calm
28	11	calm
29	11	calm
30	11	calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 54 min at the start of September to 11 h 18 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 156 minutes over September. Sunrise moves from 5:25 AM to 6:33 AM, and sunset from 7:17 PM to 5:48 PM.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Daylight (h)	13.9	13.8	13.7	13.6	13.5	13.4	13.3	13.2	13.1	13.1	13.0	12.9	12.8	12.7	12.6	12.5	12.4	12.3	12.2	12.2	12.1	12.0	11.9	11.8	11.7	11.6	11.5	11.4	11.3	11.3
Sunrise (AM)	5:25	5:28	5:30	5:32	5:35	5:37	5:39	5:42	5:44	5:46	5:49	5:51	5:53	5:56	5:58	6:00	6:02	6:05	6:07	6:09	6:12	6:14	6:16	6:19	6:21	6:24	6:26	6:28	6:31	6:33
Sunset (PM)	7:17	7:14	7:11	7:08	7:05	7:02	6:59	6:56	6:53	6:50	6:47	6:43	6:40	6:37	6:34	6:31	6:28	6:25	6:22	6:19	6:16	6:13	6:10	6:07	6:04	6:01	5:58	5:54	5:51	5:48

	Daylight (h)	Sunrise (AM)	Sunset (PM)
1	13.9	5:25	7:17
2	13.8	5:28	7:14
3	13.7	5:30	7:11
4	13.6	5:32	7:08
5	13.5	5:35	7:05
6	13.4	5:37	7:02
7	13.3	5:39	6:59
8	13.2	5:42	6:56
9	13.1	5:44	6:53
10	13.1	5:46	6:50
11	13.0	5:49	6:47
12	12.9	5:51	6:43
13	12.8	5:53	6:40
14	12.7	5:56	6:37
15	12.6	5:58	6:34
16	12.5	6:00	6:31
17	12.4	6:02	6:28
18	12.3	6:05	6:25
19	12.2	6:07	6:22
20	12.2	6:09	6:19
21	12.1	6:12	6:16
22	12.0	6:14	6:13
23	11.9	6:16	6:10
24	11.8	6:19	6:07
25	11.7	6:21	6:04
26	11.6	6:24	6:01
27	11.5	6:26	5:58
28	11.4	6:28	5:54
29	11.3	6:31	5:51
30	11.3	6:33	5:48

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 2.59 kWh/m².

For context, solar energy here swings from a low near 0.24 kWh/m² to a high of 5.78 kWh/m² in June across the year — September's 2.59 kWh/m² falls in the middle.

	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30
Solar energy (kWh/m²)	3.4	3.3	3.3	3.2	3.1	3.1	3.0	3.0	2.9	2.9	2.8	2.8	2.7	2.6	2.6	2.6	2.5	2.5	2.4	2.4	2.3	2.3	2.2	2.2	2.1	2.1	2.0	2.0	1.9	1.9
Level	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Dim	Dim	Dim

	Solar energy (kWh/m²)	Level
1	3.4	Moderate
2	3.3	Moderate
3	3.3	Moderate
4	3.2	Moderate
5	3.1	Moderate
6	3.1	Moderate
7	3.0	Moderate
8	3.0	Moderate
9	2.9	Moderate
10	2.9	Moderate
11	2.8	Moderate
12	2.8	Moderate
13	2.7	Moderate
14	2.6	Moderate
15	2.6	Moderate
16	2.6	Moderate
17	2.5	Moderate
18	2.5	Moderate
19	2.4	Moderate
20	2.4	Moderate
21	2.3	Moderate
22	2.3	Moderate
23	2.2	Moderate
24	2.2	Moderate
25	2.1	Moderate
26	2.1	Moderate
27	2.0	Moderate
28	2.0	Dim
29	1.9	Dim
30	1.9	Dim

Planning a trip in September

Is September a good time to visit Porsgrunn?

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

4.4

Sightseeing

4th-best month of the year

0.5

Beach & pool

4th-best month of the year

September is a reasonable time to visit Porsgrunn for sightseeing.

What to pack for Porsgrunn in September

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

In September, Porsgrunn sees daytime highs around 15°C and nights near 8°C. Worth packing: a warm layer and rain gear. About 12 days see rain.

a warm layerrain gear

Sea temperature near Porsgrunn in September

The nearest coast averages about 15°C in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea at the nearest coast (about 30 km away) is warmest in August at about 18°C and coldest in February near 3°C.

The water stays below 20°C all year — cool enough that most swimmers want a wetsuit.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Sea temperature (°C)	5	3	4	6	11	15	17	18	15	12	9	6
Comfort	Bracing	Bracing	Bracing	Bracing	Bracing	Bracing	Cool	Cool	Cool	Bracing	Bracing	Bracing

	Sea temperature (°C)	Comfort
Jan	5	Bracing
Feb	3	Bracing
Mar	4	Bracing
Apr	6	Bracing
May	11	Bracing
Jun	15	Bracing
Jul	17	Cool
Aug	18	Cool
Sep	15	Cool
Oct	12	Bracing
Nov	9	Bracing
Dec	6	Bracing

UV index in Porsgrunn in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 3. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Porsgrunn peaks around July 20 at about 5 (moderate) — a little sun protection helps at midday. It bottoms out near December 19 at about 0 (low).

The index reaches 3 or more — the level where the WHO recommends sun protection — in 4 months of the year.

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
UV index (midday)	0	1	2	3	4	4	5	5	3	1	0	0
Level	Low	Low	Low	Moderate	Moderate	Moderate	Moderate	Moderate	Moderate	Low	Low	Low

	UV index (midday)	Level
Jan	0	Low
Feb	1	Low
Mar	2	Low
Apr	3	Moderate
May	4	Moderate
Jun	4	Moderate
Jul	5	Moderate
Aug	5	Moderate
Sep	3	Moderate
Oct	1	Low
Nov	0	Low
Dec	0	Low

Location & terrain

Where is Porsgrunn?

Porsgrunn sits at 59.1°N, 9.7°E, 9 m above sea level, in Norway. The nearest listed city is Skien, 8.0 km away.

Topography around Porsgrunn

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Porsgrunn.

Within 3 km, the terrain around Porsgrunn has significant variations in elevation — a maximum elevation change of 254 m around an average of 48 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 548 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,422 m.

The land around Porsgrunn is covered by trees (46%) and artificial surfaces (23%) within 3 km, trees (73%) within 16 km, and trees (59%) and water (31%) within 80 km.

3 km

254 m

trees 46%

16 km

548 m

trees 73%

80 km

1,422 m

trees 59%

treesgrasslandcroplandartificial surfaceswater

← August Porsgrunn year-round climate October →Best places to visit in September

September weather nearby: Skien 8.0 km · Larvik 24 km · Sandefjord 32 km · Tønsberg 45 km · Horten 56 km · Kongsberg 59 km · Moss 66 km · Fredrikstad 73 km

Norway travel facts

Travel advisory: Level 1; Exercise Normal Precautions
Power plugs: Type C / F; 230 V · 50 Hz
Prices: ≈ 91% of US; price level, 2025
GDP per capita: $94,594; 2025
Happiness: 7.2 / 10; World Happiness, 2025
Safe drinking water: 99%; of population, 2024
Homicide rate: 0.7; per 100k, 2023
Road deaths: 2.1; per 100k/yr, 2019
Income group: High; World Bank
English: Very high; EF EPI 613
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 Porsgrunn (59.1405°, 9.6561°, elevation 9 m), 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. 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).

	Avg high (°C)	Avg low (°C)
1	18	10
2	17	10
3	17	10
4	17	10
5	17	10
6	17	9
7	17	9
8	17	9
9	16	9
10	16	9
11	16	9
12	16	9
13	16	9
14	16	8
15	15	8
16	15	8
17	15	8
18	15	8
19	15	8
20	15	8
21	14	8
22	14	7
23	14	7
24	14	7
25	14	7
26	14	7
27	13	7
28	13	7
29	13	6
30	13	6

	Clearer (%)	Cloudier (%)
1	41	59
2	40	60
3	40	60
4	41	59
5	41	59
6	41	59
7	41	59
8	41	59
9	41	59
10	41	59
11	42	58
12	42	58
13	42	58
14	42	58
15	42	58
16	42	58
17	42	58
18	42	58
19	42	58
20	42	58
21	42	58
22	41	59
23	41	59
24	41	59
25	41	59
26	41	59
27	39	61
28	39	61
29	39	61
30	39	61

	Rain chance (%)
1	42
2	41
3	41
4	41
5	41
6	41
7	41
8	41
9	41
10	41
11	41
12	41
13	41
14	40
15	40
16	39
17	39
18	38
19	37
20	37
21	36
22	36
23	36
24	36
25	36
26	36
27	37
28	37
29	38
30	38

	Dry (%)	Comfortable (%)	Humid (%)
1	86	13	1
2	87	12	1
3	88	11	1
4	89	10	1
5	91	9	0
6	91	9	0
7	92	8	0
8	92	8	0
9	93	7	0
10	93	7	0
11	93	7	0
12	94	6	0
13	94	6	0
14	95	5	0
15	95	5	0
16	96	4	0
17	96	4	0
18	96	4	0
19	96	4	0
20	97	3	0
21	97	3	0
22	97	3	0
23	97	3	0
24	97	3	0
25	98	2	0
26	98	2	0
27	98	2	0
28	98	2	0
29	98	2	0
30	98	2	0

	Avg high (°C)	Avg low (°C)
1	18	10
2	17	10
3	17	10
4	17	10
5	17	10
6	17	9
7	17	9
8	17	9
9	16	9
10	16	9
11	16	9
12	16	9
13	16	9
14	16	8
15	15	8
16	15	8
17	15	8
18	15	8
19	15	8
20	15	8
21	14	8
22	14	7
23	14	7
24	14	7
25	14	7
26	14	7
27	13	7
28	13	7
29	13	6
30	13	6

	Clearer (%)	Cloudier (%)
1	41	59
2	40	60
3	40	60
4	41	59
5	41	59
6	41	59
7	41	59
8	41	59
9	41	59
10	41	59
11	42	58
12	42	58
13	42	58
14	42	58
15	42	58
16	42	58
17	42	58
18	42	58
19	42	58
20	42	58
21	42	58
22	41	59
23	41	59
24	41	59
25	41	59
26	41	59
27	39	61
28	39	61
29	39	61
30	39	61

	Rain chance (%)
1	42
2	41
3	41
4	41
5	41
6	41
7	41
8	41
9	41
10	41
11	41
12	41
13	41
14	40
15	40
16	39
17	39
18	38
19	37
20	37
21	36
22	36
23	36
24	36
25	36
26	36
27	37
28	37
29	38
30	38

	Dry (%)	Comfortable (%)	Humid (%)
1	86	13	1
2	87	12	1
3	88	11	1
4	89	10	1
5	91	9	0
6	91	9	0
7	92	8	0
8	92	8	0
9	93	7	0
10	93	7	0
11	93	7	0
12	94	6	0
13	94	6	0
14	95	5	0
15	95	5	0
16	96	4	0
17	96	4	0
18	96	4	0
19	96	4	0
20	97	3	0
21	97	3	0
22	97	3	0
23	97	3	0
24	97	3	0
25	98	2	0
26	98	2	0
27	98	2	0
28	98	2	0
29	98	2	0
30	98	2	0

	Avg high (°C)	Avg low (°C)
1	18	10
2	17	10
3	17	10
4	17	10
5	17	10
6	17	9
7	17	9
8	17	9
9	16	9
10	16	9
11	16	9
12	16	9
13	16	9
14	16	8
15	15	8
16	15	8
17	15	8
18	15	8
19	15	8
20	15	8
21	14	8
22	14	7
23	14	7
24	14	7
25	14	7
26	14	7
27	13	7
28	13	7
29	13	6
30	13	6

	Clearer (%)	Cloudier (%)
1	41	59
2	40	60
3	40	60
4	41	59
5	41	59
6	41	59
7	41	59
8	41	59
9	41	59
10	41	59
11	42	58
12	42	58
13	42	58
14	42	58
15	42	58
16	42	58
17	42	58
18	42	58
19	42	58
20	42	58
21	42	58
22	41	59
23	41	59
24	41	59
25	41	59
26	41	59
27	39	61
28	39	61
29	39	61
30	39	61

	Rain chance (%)
1	42
2	41
3	41
4	41
5	41
6	41
7	41
8	41
9	41
10	41
11	41
12	41
13	41
14	40
15	40
16	39
17	39
18	38
19	37
20	37
21	36
22	36
23	36
24	36
25	36
26	36
27	37
28	37
29	38
30	38

	Dry (%)	Comfortable (%)	Humid (%)
1	86	13	1
2	87	12	1
3	88	11	1
4	89	10	1
5	91	9	0
6	91	9	0
7	92	8	0
8	92	8	0
9	93	7	0
10	93	7	0
11	93	7	0
12	94	6	0
13	94	6	0
14	95	5	0
15	95	5	0
16	96	4	0
17	96	4	0
18	96	4	0
19	96	4	0
20	97	3	0
21	97	3	0
22	97	3	0
23	97	3	0
24	97	3	0
25	98	2	0
26	98	2	0
27	98	2	0
28	98	2	0
29	98	2	0
30	98	2	0