São Sebastião do Caí weather in September

In September, São Sebastião do Caí sees average daytime highs of 22°C and overnight lows near 12°C, with 178 mm of rain across 12.5 wet days and about 11.8 hours of daylight. It is the 8th-warmest and 6th-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 31% of the time in September, and the air most often feels dry.

Daylight stretches from about 11 h 24 min at the start of September to 12 h 18 min by month's end. Set against the rest of the year, September is São Sebastião do Caí's 11th-clearest and 1st-windiest month. For the whole year in context, see São Sebastião do Caí's year-round climate.

Daytime high
22°
8th warmest
Overnight low
12°
5th coldest
Rainfall
178 mm
12.5 wet days
Daylight
11 h 48 min
7:25 AM – 7:15 PM
Cloud cover
62%
11th clearest
Wind
9 km/h
1st windiest
Solar energy
4.1 kWh/m²
Travel score
6.1
out of 10

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 do Caí reaches about 22°C in the afternoon and slips back to 12°C overnight — a 10°C spread between the day's warmth and the night's chill. On most days the high lands between 16°C and 28°C. Set against its neighbours, September runs about 1°C warmer than August and about 2°C cooler than October.

10°15°20°25°30°151015202530
Avg high (°C)Avg low (°C)
12212
22212
32212
42212
52212
62212
72212
82212
92212
102212
112212
122212
132212
142212
152212
162212
172212
182212
192212
202212
212212
222212
232212
242212
252212
262212
272212
282212
292213
302213

São Sebastião do Caí weather by month

How September compares with the rest of the year at a glance. September is the 8th-warmest and 6th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan29° / 19°20917.613.74.7
Feb28° / 19°18016.613.14.8
Mar27° / 18°15415.212.25.8
Apr24° / 15°14211.211.36.6
May21° / 12°13610.410.56.4
Jun19° / 10°14410.310.16.0
Jul19° / 18010.810.36.0
Aug21° / 11°14510.710.96.4
Sep22° / 12°17812.511.86.1
Oct24° / 14°21614.812.76.0
Nov26° / 16°16412.813.56.2
Dec28° / 18°18215.113.95.4

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 31% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 11% 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 (%)
14951
24852
34753
44654
54555
64357
74357
84258
94159
104159
114159
124060
134060
144060
154159
164159
174060
184060
194159
204159
214159
224159
234159
244060
254159
264060
273961
283862
293763
303664

Chance of precipitation in September

Any precipitation

São Sebastião do Caí gets around 178 mm of rain over 12.5 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 42% and peaks near 46% on the wettest days. The odds climb toward the end of the month.

0%20%40%60%151015202530
Rain chance (%)
135
236
336
437
538
638
739
839
940
1040
1141
1242
1342
1443
1543
1644
1744
1845
1945
2045
2145
2245
2345
2445
2545
2645
2746
2846
2946
3046

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 45% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
15129182
25129182
35129182
45029192
54929192
64929192
74929202
84830202
94830202
104730212
114730212
124630222
134630232
144530232
154530232
164430242
174430242
184430242
194430242
204429243
214429243
224429243
234429243
244329244
254329244
264229244
274129255
284129255
294030255
303930256

Wind in September

Winds average 9 km/h in September, the windiest month of the year.

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

051015151015202530
Wind speed (km/h)Feels
19calm
29calm
39calm
49calm
59calm
69calm
79calm
89calm
99calm
109calm
119calm
129calm
139calm
149calm
159calm
169calm
179calm
189calm
199calm
209calm
219calm
229calm
239calm
249calm
259calm
269calm
279calm
289calm
299calm
309calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 11 h 24 min at the start of September to 12 h 18 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 54 minutes over September. Sunrise moves from 7:44 AM to 7:07 AM, and sunset from 7:06 PM to 7:22 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
111.47:447:06
211.47:437:07
311.47:427:08
411.57:407:08
511.57:397:09
611.57:387:09
711.67:377:10
811.67:357:10
911.67:347:11
1011.67:337:11
1111.77:317:12
1211.77:307:12
1311.77:297:13
1411.87:287:13
1511.87:267:14
1611.87:257:15
1711.97:247:15
1811.97:237:16
1911.97:217:16
2011.97:207:17
2112.07:197:17
2212.07:177:18
2312.07:167:18
2412.17:157:19
2512.17:147:20
2612.17:127:20
2712.27:117:21
2812.27:107:21
2912.27:097:22
3012.37:077:22

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.1 kWh/m².

For context, solar energy here swings from a low near 2.41 kWh/m² to a high of 6.44 kWh/m² in December across the year — September's 4.1 kWh/m² falls in the middle.

012345151015202530
Solar energy (kWh/m²)Level
13.8Moderate
23.8Moderate
33.8Moderate
43.9Moderate
53.9Moderate
63.9Moderate
73.9Moderate
83.9Moderate
93.9Moderate
104.0Moderate
114.0Moderate
124.0Moderate
134.0Bright
144.0Bright
154.1Bright
164.1Bright
174.1Bright
184.1Bright
194.2Bright
204.2Bright
214.2Bright
224.3Bright
234.3Bright
244.3Bright
254.3Bright
264.3Bright
274.4Bright
284.4Bright
294.4Bright
304.4Bright
Planning a trip in September

Is September a good time to visit São Sebastião do Caí?

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

6.1
Sightseeing
5th-best month of the year
4.1
Beach & pool
8th-best month of the year

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

What to pack for São Sebastião do Caí in September

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

In September, São Sebastião do Caí sees daytime highs around 22°C and nights near 12°C. Worth packing: rain gear. About 13 days see rain.

rain gear

UV index in São Sebastião do Caí in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 8 — enough to warrant sun protection. The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in São Sebastião do Caí peaks around January 16 at about 13 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near June 20 at about 4 (moderate).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeVery highModerateHighVery highExtremeJan 16UV 13Jun 20UV 4
UV index (midday)Level
Jan13Extreme
Feb12Extreme
Mar10Very high
Apr8Very high
May5Moderate
Jun4Moderate
Jul4Moderate
Aug5High
Sep8Very high
Oct8Very high
Nov12Extreme
Dec13Extreme

Air quality in São Sebastião do Caí 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 do Caí is worst in September — around 17 µg/m³ PM2.5 (moderate), about 1.8× the cleanest month (December, 10 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodSep 1217 µg/m³Dec 1910 µg/m³
PM2.5 (µg/m³)Level
Jan10Good
Feb10Good
Mar10Good
Apr12Good
May12Good
Jun11Good
Jul13Moderate
Aug16Moderate
Sep17Moderate
Oct12Good
Nov11Good
Dec10Good
Location & terrain

Where is São Sebastião do Caí?

São Sebastião do Caí sits at 29.6°S, 51.4°W, 16 m above sea level, in Brazil. The nearest listed city is Montenegro, 14 km away.

Topography around São Sebastião do Caí

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

Within 3 km, the terrain around São Sebastião do Caí has only modest variations in elevation — a maximum elevation change of 107 m around an average of 32 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 512 m; within 80 km, large variations in elevation — a maximum elevation change of 988 m.

The land around São Sebastião do Caí is covered by trees (69%) within 3 km, trees (73%) within 16 km, and trees (62%) within 80 km.

3 km
107 m
16 km
512 m
80 km
988 m
treesgrasslandcroplandartificial surfaceswaterwetland
September weather nearby: Montenegro 14 km · Portão 18 km · Estância Velha 21 km · Ivoti 21 km · Novo Hamburgo 26 km · Dois Irmãos 28 km · São Leopoldo 29 km · Nova Santa Rita 31 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 do Caí (-29.5867°, -51.3756°, elevation 16 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. 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).