São Sebastião weather in September

In September, São Sebastião sees average daytime highs of 22°C and overnight lows near 19°C, with 132 mm of rain across 13.7 wet days and about 11.9 hours of daylight. It is the 10th-warmest and 7th-wettest month of the year here.

Day-to-day highs hold fairly steady near 22°C through the month. The sky is clear or mostly clear about 29% of the time in September, and the air most often feels humid.

Daylight stretches from about 11 h 30 min at the start of September to 12 h 12 min by month's end. Set against the rest of the year, September is São Sebastião's 6th-clearest and 1st-windiest month. For the whole year in context, see São Sebastião's year-round climate.

Daytime high
22°
10th warmest
Overnight low
19°
4th coldest
Rainfall
132 mm
13.7 wet days
Daylight
11 h 54 min
7:00 AM – 6:52 PM
Cloud cover
63%
6th clearest
Wind
11 km/h
1st windiest
Solar energy
4.51 kWh/m²
Travel score
6.1
out of 10

São Sebastião is settlement in Brazil.

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

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 22°C through the month.

A typical September day in São Sebastião reaches about 22°C in the afternoon and slips back to 19°C overnight — a 4°C spread between the day's warmth and the night's chill. On most days the high lands between 19°C and 26°C. Set against its neighbours, September runs on par with August and about 1°C cooler than October.

15°20°25°30°151015202530
Avg high (°C)Avg low (°C)
12218
22218
32218
42218
52218
62218
72218
82218
92218
102218
112219
122219
132219
142219
152219
162219
172219
182219
192219
202219
212219
222219
232219
242219
252219
262219
272219
282219
292219
302219

São Sebastião weather by month

How September compares with the rest of the year at a glance. September is the 10th-warmest and 7th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan27° / 24°27722.413.34.6
Feb27° / 24°22819.612.84.7
Mar27° / 23°23620.612.25.0
Apr25° / 22°13013.711.56.2
May23° / 20°11512.110.96.6
Jun23° / 18°829.510.67.0
Jul22° / 18°928.810.77.0
Aug22° / 18°758.911.27.0
Sep22° / 19°13213.711.96.1
Oct23° / 20°14715.212.65.8
Nov24° / 21°18717.513.15.6
Dec26° / 22°21419.213.45.1

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 29% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 12% of September, with mostly cloudy or overcast conditions the remaining 59%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15446
25347
35347
45149
55149
64951
74852
84753
94654
104654
114456
124456
134357
144258
154159
164060
173961
183961
193862
203763
213664
223565
233565
243367
253268
263169
273169
283169
293070
303169

Chance of precipitation in September

Any precipitation

São Sebastião gets around 132 mm of rain over 13.7 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 44% and peaks near 52% on the wettest days. The odds climb toward the end of the month.

0%20%40%60%151015202530
Rain chance (%)
134
235
335
436
537
637
738
839
939
1040
1141
1241
1342
1443
1543
1644
1745
1846
1948
2049
2149
2250
2351
2451
2551
2652
2752
2852
2952
3052

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the humid band about 42% of days. Sticky, muggy-or-worse air turns up on roughly 42% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
141549320
241548330
331547340
431547350
531546360
631445370
731445380
821445380
921445391
1021345391
1121345391
1221345401
1321244401
1421244411
1521243421
1621243421
1721242421
1821341431
1931341431
2031340432
2131340432
2231339432
2331338442
2431338443
2531337443
2631336453
2731336453
2831235454
2931235464
3031235465

Wind in September

Winds average 11 km/h in September, the windiest month of the year.

Across September, daily wind ranges from about 11 km/h on the calmest days to 12 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
111calm
211calm
311calm
411calm
511calm
611calm
711calm
811calm
911calm
1011calm
1111calm
1211calm
1311calm
1411calm
1511calm
1611calm
1711calm
1811calm
1911calm
2011calm
2111calm
2211calm
2311calm
2411calm
2511calm
2612calm
2711calm
2811calm
2911calm
3011calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 11 h 30 min at the start of September to 12 h 12 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 42 minutes over September. Sunrise moves from 7:16 AM to 6:45 AM, and sunset from 6:47 PM to 6:57 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
111.57:166:47
211.57:156:47
311.67:146:48
411.67:136:48
511.67:126:48
611.67:116:49
711.77:106:49
811.77:096:49
911.77:086:50
1011.77:066:50
1111.77:056:50
1211.87:046:51
1311.87:036:51
1411.87:026:51
1511.87:016:52
1611.97:006:52
1711.96:596:52
1811.96:586:53
1911.96:576:53
2012.06:566:53
2112.06:556:54
2212.06:546:54
2312.06:526:54
2412.16:516:55
2512.16:506:55
2612.16:496:55
2712.16:486:56
2812.16:476:56
2912.26:466:56
3012.26:456:57

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.51 kWh/m².

For context, solar energy here swings from a low near 3.22 kWh/m² to a high of 5.9 kWh/m² in December across the year — September's 4.51 kWh/m² falls in the middle.

024151015202530
Solar energy (kWh/m²)Level
14.5Bright
24.5Bright
34.5Bright
44.5Bright
54.5Bright
64.5Bright
74.5Bright
84.5Bright
94.5Bright
104.5Bright
114.5Bright
124.5Bright
134.5Bright
144.5Bright
154.5Bright
164.5Bright
174.5Bright
184.5Bright
194.5Bright
204.5Bright
214.5Bright
224.5Bright
234.5Bright
244.6Bright
254.6Bright
264.6Bright
274.6Bright
284.6Bright
294.6Bright
304.7Bright
Planning a trip in September

Is September a good time to visit São Sebastião?

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

6.1
Sightseeing
6th-best month of the year
4.4
Beach & pool
12th-best month of the year

September is a reasonable time to visit São Sebastião for sightseeing.

What to pack for São Sebastião in September

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

In September, São Sebastião sees daytime highs around 22°C and nights near 19°C. Worth packing: light clothes, rain gear and sun protection. About 14 days see rain.

light clothesrain gearsun protection

Sea temperature near São Sebastião 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 at the nearest coast (about 25 km away) is warmest in February at about 27°C and coldest in August near 21°C.

The water stays above 20°C all year — warm enough for a swim any month.

20°25°JanFebMarAprMayJunJulAugSepOctNovDeccoolrefreshingwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan26Warm
Feb27Warm
Mar27Warm
Apr26Warm
May24Refreshing
Jun22Refreshing
Jul21Refreshing
Aug21Refreshing
Sep21Refreshing
Oct22Refreshing
Nov23Refreshing
Dec25Warm

UV index in São Sebastião in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 8 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in São Sebastião peaks around February 8 at about 14 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near July 11 at about 5 (high).

The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeVery highHighVery highExtremeFeb 8UV 14Jul 11UV 5
UV index (midday)Level
Jan14Extreme
Feb14Extreme
Mar11Extreme
Apr9Very high
May7High
Jun6High
Jul5High
Aug8Very high
Sep8Very high
Oct11Extreme
Nov13Extreme
Dec14Extreme

Air quality in São Sebastião 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 São Sebastião is worst in June — around 23 µg/m³ PM2.5 (moderate), about 1.8× the cleanest month (November, 13 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateJun 2223 µg/m³Nov 2313 µg/m³
PM2.5 (µg/m³)Level
Jan13Moderate
Feb13Moderate
Mar13Moderate
Apr14Moderate
May18Moderate
Jun23Moderate
Jul23Moderate
Aug22Moderate
Sep21Moderate
Oct16Moderate
Nov13Moderate
Dec13Moderate
Location & terrain

Where is São Sebastião?

São Sebastião sits at 23.8°S, 45.4°W, 6 m above sea level, in Brazil. The nearest listed city is Ilhabela, 6.0 km away.

Topography around São Sebastião

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

Within 3 km, the terrain around São Sebastião has large variations in elevation — a maximum elevation change of 806 m around an average of 181 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,359 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,647 m.

The land around São Sebastião is covered by trees (50%) and water (39%) within 3 km, trees (53%) and water (36%) within 16 km, and water (53%) and trees (33%) within 80 km.

3 km
806 m
16 km
1,359 m
80 km
1,647 m
treesgrasslandartificial surfaceswater
September weather nearby: Ilhabela 6.0 km · Caraguatatuba 16 km · Paraibuna 49 km · Ubatuba 50 km · Salesópolis 52 km · Biritiba Mirim 67 km · Guararema 74 km · Bertioga 75 km

Brazil travel facts

Travel advisory
Level 2
Exercise Increased Caution
Power plugs
Type C / N
127 / 220 V · 60 Hz
Prices
≈ 46% of US
price level, 2025
GDP per capita
$10,713
2025
Happiness
6.6 / 10
World Happiness, 2025
Safe drinking water
89%
of population, 2024
Homicide rate
19.3
per 100k, 2023
Road deaths
16
per 100k/yr, 2019
Income group
Upper middle
World Bank
English
Low
EF EPI 482
Religion
Roman Catholic 57%Evangelical 27%none 9%other 4%

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 São Sebastião (-23.76°, -45.4097°, elevation 6 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. 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).