San Sebastian weather in September

In September, San Sebastian sees average daytime highs of 21°C and overnight lows near 15°C, with 96 mm of rain across 13 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 22°C in the first days to 19°C by the end. The sky is clear or mostly clear about 32% of the time in September, and the air most often feels comfortable.

Daylight stretches from about 13 hours at the start of September to 11 h 36 min by month's end. Set against the rest of the year, September is San Sebastian's 2nd-clearest and 9th-windiest month. For the whole year in context, see San Sebastian's year-round climate.

Daytime high
21°
3rd warmest
Overnight low
15°
10th coldest
Rainfall
96 mm
13 wet days
Daylight
12 h 18 min
6:53 AM – 7:11 PM
Cloud cover
55%
2nd clearest
Wind
10 km/h
9th windiest
Solar energy
4.17 kWh/m²
Travel score
6.0
out of 10

San Sebastian is capital city of the homonymous municipality of Comarca de San Sebastián, Spain.

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 22°C in the first days to 19°C by the end.

A typical September day in San Sebastian reaches about 21°C in the afternoon and slips back to 15°C overnight — a 6°C spread between the day's warmth and the night's chill. On most days the high lands between 17°C and 25°C. Set against its neighbours, September runs about 2°C cooler than August and about 3°C warmer than October.

10°15°20°25°30°151015202530
Avg high (°C)Avg low (°C)
12216
22216
32216
42216
52115
62115
72115
82115
92115
102115
112115
122115
132115
142115
152115
162115
172015
182015
192014
202014
212014
222014
232014
242014
252014
262014
272014
282014
291914
301914

San Sebastian 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 (°C)Rainfall (mm)Wet daysSnow daysDaylight (hours)Travel score
Jan10° / 13515.41.29.22.1
Feb11° / 122141.910.22.3
Mar13° / 11513.90.911.63.2
Apr14° / 12716.10.113.23.5
May17° / 11°11715.4014.54.8
Jun20° / 14°9312.7015.15.8
Jul22° / 16°8212.7014.96.3
Aug23° / 17°8912.9013.86.5
Sep21° / 15°9613012.36.0
Oct18° / 12°12814.3010.85.2
Nov13° / 17015.70.29.53.3
Dec11° / 13815.10.88.82.4

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 32% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 18% of September, with mostly cloudy or overcast conditions the remaining 50%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15446
25446
35545
45545
55545
65446
75446
85446
95347
105347
115347
125248
135248
145149
154951
164951
174852
184852
194753
204852
214852
224852
234753
244753
254753
264654
274654
284456
294456
304456

Chance of precipitation in September

Any precipitation

San Sebastian gets around 96 mm of rain over 13 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 44% and peaks near 47% on the wettest days. The odds climb toward the end of the month.

0%20%40%60%151015202530
Rain chance (%)
141
241
341
441
541
641
741
841
942
1042
1142
1243
1343
1444
1544
1645
1745
1846
1946
2046
2146
2246
2346
2446
2547
2647
2747
2847
2947
3047

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the comfortable band about 36% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
120343511
222343411
323343310
42434339
52534328
62635328
72735317
82835317
92935306
103035306
113135305
123134295
133234294
143335294
153435283
163535273
173635262
183736252
193836241
203937231
214037221
224138211
234139191
244239180
254339180
264439170
274539160
284639150
294739140
304938130

Wind in September

Winds average 10 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.

051015151015202530
Wind speed (km/h)Feels
110calm
210calm
310calm
410calm
510calm
610calm
710calm
810calm
910calm
1010calm
1110calm
1210calm
1310calm
1410calm
1510calm
1610calm
1710calm
1811calm
1911calm
2011calm
2111calm
2211calm
2311calm
2411calm
2511calm
2611calm
2711calm
2811calm
2911calm
3011calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 13 hours 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 84 minutes over September. Sunrise moves from 6:36 AM to 7:10 AM, and sunset from 7:39 PM to 6:45 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
113.06:367:39
213.06:387:37
312.96:397:35
412.96:407:33
512.86:417:32
612.86:427:30
712.76:437:28
812.76:447:26
912.66:457:24
1012.66:477:22
1112.56:487:20
1212.56:497:19
1312.46:507:17
1412.46:517:15
1512.36:527:13
1612.36:537:11
1712.26:557:09
1812.26:567:07
1912.16:577:05
2012.16:587:03
2112.06:597:02
2212.07:007:00
2311.97:026:58
2411.97:036:56
2511.87:046:54
2611.87:056:52
2711.77:066:50
2811.77:076:48
2911.67:096:47
3011.67:106:45

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.17 kWh/m².

For context, solar energy here swings from a low near 1.38 kWh/m² to a high of 5.87 kWh/m² in June across the year — September's 4.17 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.7Bright
24.7Bright
34.7Bright
44.6Bright
54.6Bright
64.6Bright
74.5Bright
84.5Bright
94.4Bright
104.4Bright
114.3Bright
124.3Bright
134.2Bright
144.2Bright
154.1Bright
164.1Bright
174.0Bright
184.0Bright
194.0Moderate
203.9Moderate
213.9Moderate
223.8Moderate
233.8Moderate
243.7Moderate
253.7Moderate
263.6Moderate
273.6Moderate
283.6Moderate
293.5Moderate
303.5Moderate
Planning a trip in September

Is September a good time to visit San Sebastian?

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

6.0
Sightseeing
3rd-best month of the year
3.4
Beach & pool
3rd-best month of the year

September is a reasonable time to visit San Sebastian for sightseeing.

What to pack for San Sebastian in September

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

In September, San Sebastian sees daytime highs around 21°C and nights near 15°C. Worth packing: rain gear. About 13 days see rain.

rain gear

Sea temperature near San Sebastian in September

The nearest coast averages about 21°C 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 22°C and coldest in February near 12°C.

It's comfortable for a long swim from Jul 1 to Sep 25 — about 2.9 months when the water holds above 20°C.

10°15°20°25°JanFebMarAprMayJunJulAugSepOctNovDecbracingcoolrefreshingwarmcomfortable to swim
Sea temperature (°C)Comfort
Jan13Bracing
Feb12Bracing
Mar13Bracing
Apr14Bracing
May16Cool
Jun19Cool
Jul21Refreshing
Aug22Refreshing
Sep21Refreshing
Oct18Cool
Nov16Cool
Dec14Bracing

UV index in San Sebastian in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 5 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in San Sebastian peaks around July 15 at about 8 (very high) — sunscreen, a hat and midday shade are essential. It bottoms out near December 22 at about 1 (low).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecLowModerateHighVery highHighModerateLowJul 15UV 8Dec 22UV 1
UV index (midday)Level
Jan2Low
Feb2Low
Mar5Moderate
Apr6High
May6High
Jun8Very high
Jul9Very high
Aug8Very high
Sep5High
Oct4Moderate
Nov2Low
Dec1Low
Location & terrain

Where is San Sebastian?

San Sebastian sits at 43.3°N, 2.0°W, 17 m above sea level, in Spain. The nearest listed city is Pasaia, 4.0 km away.

Topography around San Sebastian

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

Within 3 km, the terrain around San Sebastian has only modest variations in elevation — a maximum elevation change of 231 m around an average of 45 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 839 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,533 m.

The land around San Sebastian is covered by trees (39%), artificial surfaces (34%) and water (21%) within 3 km, trees (42%) and water (42%) within 16 km, and trees (47%) and water (27%) within 80 km.

3 km
231 m
16 km
839 m
80 km
1,533 m
treesgrasslandcroplandartificial surfacesbare terrainwater
September weather nearby: Pasaia 4.0 km · Hernani 5.0 km · Errenteria 6.0 km · Lasarte 6.0 km · Oria 7.0 km · Irun 15 km · Hondarribia 16 km · Zarautz 16 km

Spain travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type C / F
230 V · 50 Hz
Prices
≈ 65% of US
price level, 2025
GDP per capita
$38,627
2025
Happiness
6.5 / 10
World Happiness, 2025
Safe drinking water
99%
of population, 2024
Homicide rate
0.7
per 100k, 2023
Road deaths
3.9
per 100k/yr, 2019
Income group
High
World Bank
English
Moderate
EF EPI 540
Religion
Roman Catholic 58%atheist 16%agnostic 11%non-believer 11%

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 San Sebastian (43.3128°, -1.975°, elevation 17 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).