Rosário weather in September

In September, Rosário sees average daytime highs of 34°C and overnight lows near 25°C, with 10 mm of rain across 2.6 wet days and about 12 hours of daylight. It is the 2nd-warmest and 12th-wettest month of the year here.

Day-to-day highs hold fairly steady near 34°C through the month. The sky is clear or mostly clear about 59% of the time in September, and the air most often feels oppressive.

Daylight stretches from about 11 h 54 min at the start of September to 12 hours by month's end. Set against the rest of the year, September is Rosário's 2nd-clearest and 2nd-windiest month. For the whole year in context, see Rosário's year-round climate.

Daytime high
34°
2nd warmest
Overnight low
25°
9th coldest
Rainfall
10 mm
2.6 wet days
Daylight
12 hours
5:52 AM – 5:51 PM
Cloud cover
39%
2nd clearest
Wind
12 km/h
2nd windiest
Solar energy
6.21 kWh/m²
Travel score
3.6
out of 10

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 34°C through the month.

A typical September day in Rosário reaches about 34°C in the afternoon and slips back to 25°C overnight — a 9°C spread between the day's warmth and the night's chill. On most days the high lands between 32°C and 36°C. Set against its neighbours, September runs about 1°C warmer than August and on par with October.

20°25°30°35°40°151015202530
Avg high (°C)Avg low (°C)
13424
23424
33424
43424
53424
63424
73425
83425
93425
103425
113425
123425
133425
143425
153425
163425
173425
183425
193425
203425
213425
223425
233425
243425
253425
263425
273425
283425
293425
303425

How September really feels in Rosário

Once humidity and wind are folded in, September averages 30 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
30
heat index over the day's high
Days feeling ≤ C
0
wind chill below the day's low

The story in September is heat — humidity pushes the afternoon "feels like" well above the raw temperature.

Rosário weather by month

How September compares with the rest of the year at a glance. September is the 2nd-warmest and 12th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan32° / 24°26225.412.22.6
Feb31° / 24°33025.612.12.5
Mar31° / 24°43730122.4
Apr31° / 24°42628.411.92.5
May31° / 24°25524.111.93.0
Jun31° / 24°9615.711.83.9
Jul31° / 23°579.711.84.5
Aug33° / 24°164.311.94.2
Sep34° / 25°102.6123.6
Oct34° / 25°214.812.13.4
Nov34° / 25°437.112.13.3
Dec33° / 25°9815.412.23.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 59% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 31% of September, with mostly cloudy or overcast conditions the remaining 11%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
1919
2919
3919
4928
5928
6928
7919
89010
99010
109010
119010
129010
139010
148911
158911
168911
178911
188812
198812
208812
218812
228812
238812
248812
258812
268812
278812
288812
298812
308713

Chance of precipitation in September

Any precipitation

Rosário gets around 10 mm of rain over 2.6 wet days in September, the driest month. The line is the day-by-day chance of measurable precipitation.

Day to day, the chance of measurable rain averages around 9% and peaks near 12% on the wettest days.

0%10%20%30%151015202530
Rain chance (%)
19
29
39
48
58
68
77
87
97
107
118
128
138
148
158
169
179
189
1910
2010
2110
2210
2311
2411
2511
2611
2711
2812
2912
3012

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the oppressive band about 87% of days. Sticky, muggy-or-worse air turns up on roughly 100% of them.

0%25%50%75%100%151015202530
Muggy (%)Oppressive (%)Miserable (%)
112871
212871
313861
413861
514851
614851
715841
815850
915850
1015850
1115850
1215850
1315850
1415850
1514860
1614860
1713870
1813870
1913870
2012880
2112880
2211890
2311890
2410900
2510900
2610900
279910
289910
299910
308920

Wind in September

Winds average 12 km/h in September.

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
812calm
912calm
1012calm
1112calm
1212calm
1312calm
1412calm
1512calm
1612calm
1712calm
1812light breeze
1912light breeze
2012light breeze
2112light breeze
2212light breeze
2312light breeze
2412light breeze
2512light breeze
2612light breeze
2712light breeze
2812light breeze
2912light breeze
3012light breeze

Sunrise & sunset in September

DaylightNight

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

Days grow by about 6 minutes over September. Sunrise moves from 5:58 AM to 5:46 AM, and sunset from 5:55 PM to 5:47 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
111.95:585:55
211.95:585:55
311.95:585:54
412.05:575:54
512.05:575:54
612.05:565:54
712.05:565:53
812.05:555:53
912.05:555:53
1012.05:555:53
1112.05:545:52
1212.05:545:52
1312.05:535:52
1412.05:535:51
1512.05:525:51
1612.05:525:51
1712.05:515:51
1812.05:515:50
1912.05:505:50
2012.05:505:50
2112.05:505:49
2212.05:495:49
2312.05:495:49
2412.05:485:49
2512.05:485:48
2612.05:475:48
2712.05:475:48
2812.05:465:47
2912.05:465:47
3012.05:465:47

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 6.21 kWh/m².

For context, solar energy here swings from a low near 4.38 kWh/m² to a high of 6.27 kWh/m² in October across the year — September's 6.21 kWh/m² sits near the top of that range.

0246151015202530
Solar energy (kWh/m²)Level
16.0Intense
26.1Intense
36.1Intense
46.1Intense
56.1Intense
66.1Intense
76.1Intense
86.2Intense
96.2Intense
106.2Intense
116.2Intense
126.2Intense
136.2Intense
146.2Intense
156.2Intense
166.2Intense
176.2Intense
186.2Intense
196.2Intense
206.2Intense
216.2Intense
226.3Intense
236.3Intense
246.3Intense
256.3Intense
266.3Intense
276.3Intense
286.3Intense
296.3Intense
306.3Intense
Planning a trip in September

Hazard calendar for Rosário

In seasonPeak

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

Rosário's monsoon runs January–May, when most of the year's rain falls.

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

Is September a good time to visit Rosário?

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

3.6
Sightseeing
4th-best month of the year
7.2
Beach & pool
2nd-best month of the year

September is a weaker month for outdoor sightseeing in Rosário. The water and warmth also suit a beach or pool day.

What to pack for Rosário in September

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

In September, Rosário sees daytime highs around 34°C and nights near 25°C. Pack light clothes and sun protection.

light clothessun protection

Sea temperature near Rosário in September

The nearest coast averages about 28°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 38 km away) is warmest in May at about 29°C and coldest in October near 28°C.

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

26°28°30°JanFebMarAprMayJunJulAugSepOctNovDecwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan28Tropical
Feb28Tropical
Mar28Tropical
Apr29Tropical
May29Tropical
Jun29Tropical
Jul28Tropical
Aug28Tropical
Sep28Warm
Oct28Warm
Nov28Warm
Dec28Warm

UV index in Rosário in September

LowModerateHighVery highExtreme

Clear-sky midday UV in September peaks around 12 (very high — sun protection essential). The full-year curve, shaded by WHO exposure level, is below.

Under clear skies, the midday UV index in Rosário peaks around March 18 at about 15 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near July 17 at about 10 (extreme).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeMar 18UV 15Jul 17UV 10
UV index (midday)Level
Jan13Extreme
Feb14Extreme
Mar16Extreme
Apr14Extreme
May11Extreme
Jun10Extreme
Jul10Very high
Aug10Extreme
Sep12Extreme
Oct12Extreme
Nov11Extreme
Dec11Extreme

Air quality in Rosário 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 Rosário is worst in February — around 17 µg/m³ PM2.5 (moderate), about 1.9× the cleanest month (June, 9 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateFeb 2017 µg/m³Jun 149 µg/m³
PM2.5 (µg/m³)Level
Jan15Moderate
Feb17Moderate
Mar17Moderate
Apr14Moderate
May10Good
Jun9Good
Jul11Good
Aug10Good
Sep10Good
Oct12Moderate
Nov14Moderate
Dec14Moderate
Location & terrain

Where is Rosário?

Rosário sits at 2.9°S, 44.2°W, 1 m above sea level, in Brazil. The nearest listed city is Bacabeira, 8.0 km away.

Topography around Rosário

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

Within 3 km, the terrain around Rosário has only modest variations in elevation — a maximum elevation change of 43 m around an average of 14 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 97 m; within 80 km, only modest variations in elevation — a maximum elevation change of 124 m.

The land around Rosário is covered by trees (57%) and grassland (25%) within 3 km, trees (58%) within 16 km, and trees (44%) within 80 km.

3 km
43 m
16 km
97 m
80 km
124 m
treesshrubsgrasslandartificial surfaceswaterwetlandmangroves
September weather nearby: Bacabeira 8.0 km · Santa Rita 24 km · Morros 25 km · Icatu 27 km · São Luís 46 km · São José de Ribamar 48 km · Paço do Lumiar 48 km · Itapecuru Mirim 52 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 Rosário (-2.9405°, -44.249°, elevation 1 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).