Norrtälje weather in September

In September, Norrtälje sees average daytime highs of 15°C and overnight lows near 9°C, with 50 mm of rain across 9 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 23% 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 12 min by month's end. Set against the rest of the year, September is Norrtälje's 6th-clearest and 7th-windiest month. For the whole year in context, see Norrtälje's year-round climate.

Daytime high
15°
4th warmest
Overnight low
9th coldest
Rainfall
50 mm
9 wet days
Daylight
12 h 30 min
5:24 AM – 5:55 PM
Cloud cover
63%
6th clearest
Wind
15 km/h
7th windiest
Solar energy
2.69 kWh/m²
Travel score
4.6
out of 10

Norrtälje is urban area in Norrtälje Municipality, Sweden.

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 17°C in the first days to 13°C by the end.

A typical September day in Norrtälje reaches about 15°C in the afternoon and slips back to 9°C overnight — a 6°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 5°C cooler than August and about 6°C warmer than October.

10°15°20°25°151015202530
Avg high (°C)Avg low (°C)
11812
21711
31711
41711
51711
61711
71711
81711
91610
101610
111610
121610
131610
141610
151510
16159
17159
18159
19159
20149
21149
22149
23148
24148
25148
26138
27138
28138
29138
30137

How September really feels in Norrtälje

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
0
heat index over the day's high
Days feeling ≤ C
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.

Norrtälje 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.

MonthHigh / Low (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan / -3°368.66.56.50.0
Feb / -4°297.378.70.0
Mar / -2°297.4511.30.0
Apr / 317.8214.11.4
May13° / 398.50.116.73.8
Jun17° / 10°5910018.25.5
Jul20° / 13°6210.2017.66.4
Aug20° / 13°6411.5015.36.0
Sep15° / 509012.64.6
Oct10° / 509.70.39.82.0
Nov / 4910.73.17.20.2
Dec / -2°4610.86.45.80.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 23% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 19% of September, with mostly cloudy or overcast conditions the remaining 59%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
13961
24060
34060
44060
54159
64159
74258
84258
94357
104357
114357
124258
134258
144357
154357
164258
174258
184258
194258
204159
214159
224060
234060
244060
254159
264159
274060
283961
293961
303961

Chance of precipitation in September

Any precipitation

Norrtälje gets around 50 mm of rain over 9 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 31% and peaks near 35% on the wettest days.

0%10%20%30%40%50%151015202530
Rain chance (%)
135
234
334
433
533
632
732
832
932
1032
1132
1232
1332
1432
1531
1631
1731
1831
1930
2030
2129
2229
2329
2428
2528
2628
2728
2828
2928
3028

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 88% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)
169265
271254
373243
474233
577212
678202
780191
881181
983161
1085150
1186140
1288120
1389110
1490100
159190
169280
179370
189460
199460
209550
219640
229640
239640
249730
259730
269730
279730
289820
299820
309820

Wind in September

Winds average 15 km/h in September.

Across September, daily wind ranges from about 14 km/h on the calmest days to 15 km/h at its breeziest. It stays fairly steady from day to day.

05101520151015202530
Wind speed (km/h)Feels
114light breeze
214light breeze
314light breeze
415light breeze
515light breeze
615light breeze
715light breeze
815light breeze
915light breeze
1015light breeze
1115light breeze
1215light breeze
1315light breeze
1415light breeze
1515light breeze
1615light breeze
1715light breeze
1815light breeze
1915light breeze
2015light breeze
2115light breeze
2215light breeze
2315light breeze
2415light breeze
2515light breeze
2615light breeze
2715light breeze
2815light breeze
2915light breeze
3015light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 h 54 min at the start of September to 11 h 12 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 162 minutes over September. Sunrise moves from 4:48 AM to 5:57 AM, and sunset from 6:42 PM to 5:12 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.94:486:42
213.84:506:39
313.74:526:36
413.64:556:33
513.54:576:30
613.55:006:27
713.45:026:24
813.35:046:20
913.25:076:17
1013.15:096:14
1113.05:126:11
1212.95:146:08
1312.85:166:05
1412.75:196:02
1512.65:215:59
1612.55:245:55
1712.45:265:52
1812.35:285:49
1912.35:315:46
2012.25:335:43
2112.15:365:40
2212.05:385:37
2311.95:405:33
2411.85:435:30
2511.75:455:27
2611.65:485:24
2711.55:505:21
2811.45:525:18
2911.35:555:15
3011.25:575:12

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 2.69 kWh/m².

For context, solar energy here swings from a low near 0.19 kWh/m² to a high of 5.93 kWh/m² in June across the year — September's 2.69 kWh/m² falls in the middle.

01234151015202530
Solar energy (kWh/m²)Level
13.4Moderate
23.4Moderate
33.3Moderate
43.3Moderate
53.2Moderate
63.2Moderate
73.1Moderate
83.1Moderate
93.0Moderate
103.0Moderate
112.9Moderate
122.9Moderate
132.8Moderate
142.8Moderate
152.7Moderate
162.7Moderate
172.6Moderate
182.6Moderate
192.5Moderate
202.5Moderate
212.4Moderate
222.4Moderate
232.3Moderate
242.3Moderate
252.2Moderate
262.2Moderate
272.1Moderate
282.1Moderate
292.0Moderate
301.9Dim
Planning a trip in September

Is September a good time to visit Norrtälje?

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

4.6
Sightseeing
4th-best month of the year
0.5
Beach & pool
4th-best month of the year

September is a reasonable time to visit Norrtälje for sightseeing.

What to pack for Norrtälje in September

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

In September, Norrtälje sees daytime highs around 15°C and nights near 9°C. Worth packing: a warm layer and rain gear. About 9 days see rain.

a warm layerrain gear

Sea temperature near Norrtälje in September

The nearest coast averages about 14°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 18 km away) is warmest in August at about 17°C and coldest in February near 1°C.

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

0°5°10°15°20°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshing
Sea temperature (°C)Comfort
Jan3Bracing
Feb1Bracing
Mar2Bracing
Apr3Bracing
May6Bracing
Jun11Bracing
Jul16Cool
Aug17Cool
Sep14Bracing
Oct10Bracing
Nov7Bracing
Dec4Bracing

UV index in Norrtälje 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 Norrtälje peaks around June 17 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.

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateLowJun 17UV 5Dec 19UV 0
UV index (midday)Level
Jan0Low
Feb1Low
Mar2Low
Apr3Moderate
May4Moderate
Jun5Moderate
Jul5Moderate
Aug4Moderate
Sep3Moderate
Oct1Low
Nov0Low
Dec0Low
Location & terrain

Where is Norrtälje?

Norrtälje sits at 59.8°N, 18.7°E, 13 m above sea level, in Sweden. The nearest listed city is Åkersberga, 38 km away.

Topography around Norrtälje

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

Within 3 km, the terrain around Norrtälje has only modest variations in elevation — a maximum elevation change of 51 m around an average of 17 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 68 m; within 80 km, only modest variations in elevation — a maximum elevation change of 111 m.

The land around Norrtälje is covered by trees (43%) and grassland (23%) within 3 km, trees (61%) within 16 km, and water (53%) and trees (35%) within 80 km.

3 km
51 m
16 km
68 m
80 km
111 m
treesgrasslandcroplandartificial surfaceswaterwetland
September weather nearby: Åkersberga 38 km · Vallentuna 43 km · Täby 50 km · Märsta 50 km · Gustavsberg 51 km · Upplands Väsby 52 km · Boo 53 km · Lidingö 54 km

Sweden travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type C / F
230 V · 50 Hz
Prices
≈ 87% of US
price level, 2025
GDP per capita
$63,133
2025
Happiness
7.3 / 10
World Happiness, 2025
Safe drinking water
100%
of population, 2024
Homicide rate
1.1
per 100k, 2023
Road deaths
3.1
per 100k/yr, 2019
Income group
High
World Bank
English
Very high
EF EPI 609
Religion
Church of Sweden 54%none or unspecified 37%other 9%

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 Norrtälje (59.758°, 18.705°, elevation 13 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).