Rio das Ostras weather in September

In September, Rio das Ostras sees average daytime highs of 26°C and overnight lows near 19°C, with 73 mm of rain across 10.1 wet days and about 11.9 hours of daylight. It is the 8th-warmest and 8th-wettest month of the year here.

Day-to-day highs hold fairly steady near 26°C through the month. The sky is clear or mostly clear about 37% of the time in September, and the air most often feels muggy.

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 Rio das Ostras's 6th-clearest and 1st-windiest month. For the whole year in context, see Rio das Ostras's year-round climate.

Daytime high
26°
8th warmest
Overnight low
19°
4th coldest
Rainfall
73 mm
10.1 wet days
Daylight
11 h 54 min
6:46 AM – 6:38 PM
Cloud cover
56%
6th clearest
Wind
13 km/h
1st windiest
Solar energy
4.91 kWh/m²
Travel score
6.7
out of 10

Rio das Ostras is human 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 26°C through the month.

A typical September day in Rio das Ostras reaches about 26°C in the afternoon and slips back to 19°C overnight — a 7°C spread between the day's warmth and the night's chill. On most days the high lands between 22°C and 31°C. Set against its neighbours, September runs on par with August and on par with October.

15°20°25°30°35°151015202530
Avg high (°C)Avg low (°C)
12619
22619
32619
42619
52619
62619
72619
82619
92619
102619
112619
122619
132619
142619
152619
162619
172619
182619
192619
202619
212619
222619
232619
242619
252619
262620
272620
282620
292620
302620

How September really feels in Rio das Ostras

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.

Rio das Ostras weather by month

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

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan30° / 23°20616.613.24.1
Feb31° / 24°13612.712.84.2
Mar30° / 23°17217.812.24.3
Apr28° / 21°851211.55.7
May26° / 19°609.510.96.9
Jun26° / 18°315.910.67.6
Jul25° / 18°295.610.87.8
Aug26° / 18°346.311.27.6
Sep26° / 19°7310.111.96.7
Oct27° / 20°1081212.56.1
Nov27° / 21°20317.513.15.1
Dec29° / 23°2221913.44.2

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 37% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 13% of September, with mostly cloudy or overcast conditions the remaining 51%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
16436
26436
36436
46337
56238
66139
76040
85941
95743
105545
115446
125248
135149
145050
154852
164753
174555
184555
194456
204357
214258
224258
234159
243961
253961
263961
273961
283862
293862
303862

Chance of precipitation in September

Any precipitation

Rio das Ostras gets around 73 mm of rain over 10.1 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 33% and peaks near 41% on the wettest days. The odds climb toward the end of the month.

0%10%20%30%40%50%151015202530
Rain chance (%)
124
224
325
425
526
626
727
828
929
1029
1130
1230
1331
1432
1532
1633
1734
1835
1936
2037
2138
2238
2339
2439
2540
2640
2741
2841
2941
3041

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the muggy band about 46% of days. Sticky, muggy-or-worse air turns up on roughly 51% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
121442411
211442421
311442421
411442421
511442421
611441421
711441421
811441431
911341431
1011340442
1111340452
1211240462
1311239462
1411138473
1501138483
1611037493
1711036504
1811035504
1911035505
2011034505
211933516
221933507
231932498
242932499
2529314810
2629314811
2729304712
2829304713
2929304613
3029304514

Wind in September

Winds average 13 km/h in September, the windiest month of the year.

Across September, daily wind ranges from about 12 km/h on the calmest days to 13 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
112light breeze
212light breeze
312light breeze
413light breeze
513light breeze
613light breeze
713light breeze
813light breeze
913light breeze
1013light breeze
1113light breeze
1213light breeze
1313light breeze
1413light breeze
1513light breeze
1613light breeze
1713light breeze
1813light breeze
1913light breeze
2013light breeze
2113light breeze
2213light breeze
2313light breeze
2413light breeze
2513light breeze
2612light breeze
2712light breeze
2812light breeze
2912light breeze
3012light breeze

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 7:01 AM to 6:32 AM, and sunset from 6:34 PM to 6:43 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
111.57:016:34
211.67:006:34
311.66:596:34
411.66:586:35
511.66:576:35
611.76:566:35
711.76:556:36
811.76:546:36
911.76:536:36
1011.76:526:36
1111.86:516:37
1211.86:506:37
1311.86:496:37
1411.86:486:38
1511.86:476:38
1611.96:466:38
1711.96:456:39
1811.96:446:39
1911.96:436:39
2012.06:426:39
2112.06:416:40
2212.06:406:40
2312.06:396:40
2412.16:386:41
2512.16:376:41
2612.16:366:41
2712.16:356:42
2812.16:346:42
2912.26:336:42
3012.26:326:43

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.91 kWh/m².

For context, solar energy here swings from a low near 3.54 kWh/m² to a high of 6.31 kWh/m² in February across the year — September's 4.91 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
14.8Bright
24.8Bright
34.8Bright
44.9Bright
54.9Bright
64.9Bright
74.9Bright
84.9Bright
94.9Bright
104.9Bright
114.9Bright
124.9Bright
134.9Bright
144.9Bright
154.9Bright
164.9Bright
174.9Bright
184.9Bright
194.9Bright
204.9Bright
215.0Bright
225.0Bright
235.0Bright
245.0Bright
255.0Bright
265.0Bright
275.0Bright
285.0Bright
295.0Bright
305.1Bright
Planning a trip in September

Hazard calendar for Rio das Ostras

In seasonPeak

None of Rio das Ostras's seasonal hazards are active in September. The full-year calendar below shows when the rainy season, cyclone risk and dust haze do peak.

Rio das Ostras's rainy season runs October–March, when most of the year's rain falls.

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

Is September a good time to visit Rio das Ostras?

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

6.7
Sightseeing
5th-best month of the year
6.5
Beach & pool
6th-best month of the year

September is a reasonable time to visit Rio das Ostras for sightseeing. The water and warmth also suit a beach or pool day.

What to pack for Rio das Ostras in September

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

In September, Rio das Ostras sees daytime highs around 26°C and nights near 19°C. Worth packing: light clothes, rain gear and sun protection. About 10 days see rain.

light clothesrain gearsun protection

Sea temperature near Rio das Ostras 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 13 km away) is warmest in March at about 25°C and coldest in September near 21°C.

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

20°22°24°26°JanFebMarAprMayJunJulAugSepOctNovDeccoolrefreshingwarmcomfortable to swim
Sea temperature (°C)Comfort
Jan24Refreshing
Feb24Warm
Mar25Warm
Apr25Warm
May24Refreshing
Jun23Refreshing
Jul22Refreshing
Aug22Refreshing
Sep21Refreshing
Oct22Refreshing
Nov22Refreshing
Dec24Refreshing

UV index in Rio das Ostras 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 Rio das Ostras peaks around January 16 at about 14 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near July 11 at about 6 (high).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeVery highHighVery highExtremeJan 16UV 14Jul 11UV 6
UV index (midday)Level
Jan14Extreme
Feb14Extreme
Mar13Extreme
Apr9Very high
May7High
Jun6High
Jul6High
Aug8Very high
Sep8Very high
Oct12Extreme
Nov14Extreme
Dec14Extreme
Location & terrain

Where is Rio das Ostras?

Rio das Ostras sits at 22.5°S, 41.9°W, 11 m above sea level, in Brazil. The nearest listed city is Macaé, 23 km away.

Topography around Rio das Ostras

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

Within 3 km, the terrain around Rio das Ostras has only modest variations in elevation — a maximum elevation change of 49 m around an average of 4 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 693 m; within 80 km, very significant variations in elevation — a maximum elevation change of 2,215 m.

The land around Rio das Ostras is covered by water (39%) and artificial surfaces (32%) within 3 km, water (45%) and grassland (27%) within 16 km, and water (37%), trees (31%) and grassland (28%) within 80 km.

3 km
49 m
16 km
693 m
80 km
2,215 m
treesgrasslandartificial surfacesbare terrainwaterwetlandmangroves
September weather nearby: Macaé 23 km · Buzios 25 km · Casimiro de Abreu 27 km · São Pedro da Aldeia 38 km · Cabo Frio 41 km · Iguaba Grande 45 km · Silva Jardim 48 km · Arraial do Cabo 50 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 Rio das Ostras (-22.5269°, -41.945°, elevation 11 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).