Rio Negro weather in September

In September, Rio Negro sees average daytime highs of 22°C and overnight lows near 12°C, with 145 mm of rain across 10.8 wet days and about 11.8 hours of daylight. It is the 8th-warmest and 4th-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 28% of the time in September, and the air most often feels dry.

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

Daytime high
22°
8th warmest
Overnight low
12°
5th coldest
Rainfall
145 mm
10.8 wet days
Daylight
11 h 48 min
7:18 AM – 7:09 PM
Cloud cover
66%
6th clearest
Wind
11 km/h
1st windiest
Solar energy
4.16 kWh/m²
Travel score
6.4
out of 10

Rio Negro 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 Rio Negro 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 29°C. Set against its neighbours, September runs about 1°C warmer than August and about 1°C cooler than October.

10°15°20°25°30°151015202530
Avg high (°C)Avg low (°C)
12211
22212
32212
42212
52212
62212
72212
82212
92212
102212
112212
122212
132212
142212
152212
162212
172212
182212
192212
202213
212213
222213
232213
242213
252213
262213
272213
282213
292213
302213

Rio Negro weather by month

How September compares with the rest of the year at a glance. September is the 8th-warmest and 4th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan27° / 18°18319.913.54.9
Feb27° / 18°15717.812.95.0
Mar26° / 17°10614.212.25.9
Apr24° / 15°718.811.46.9
May21° / 12°94810.76.6
Jun19° / 10°1069.210.46.3
Jul19° / 86810.56.5
Aug21° / 10°847.811.17.0
Sep22° / 12°14510.811.86.4
Oct23° / 14°14414.212.66.0
Nov25° / 15°12313.913.36.0
Dec26° / 17°1491713.65.4

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 28% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 10% of September, with mostly cloudy or overcast conditions the remaining 62%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15347
25248
35050
45050
54852
64654
74555
84456
94258
104258
114159
124060
133961
143961
153763
163763
173664
183565
193565
203466
213466
223367
233268
243169
253070
262971
272971
282872
292872
302872

Chance of precipitation in September

Any precipitation

Rio Negro gets around 145 mm of rain over 10.8 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 35% and peaks near 44% on the wettest days. The odds climb toward the end of the month.

0%10%20%30%40%50%151015202530
Rain chance (%)
126
226
327
427
528
628
729
830
931
1031
1132
1233
1334
1434
1535
1636
1737
1838
1938
2039
2140
2241
2341
2442
2542
2643
2743
2844
2944
3044

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 49% of days. It rarely turns muggy — the humid and sticky bands barely register.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)
1593650
2573760
3573760
4553870
5553870
6533980
7533980
8533980
9514090
10514090
11514090
125040100
134940101
144940111
154940111
164839121
174839121
184839121
194838131
204838131
214838141
224737141
234737151
244637161
254537171
264437181
274338191
284238201
294138201
304038211

Wind in September

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

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
311calm
411calm
511calm
611calm
711calm
811calm
911calm
1011calm
1111calm
1211calm
1311calm
1411calm
1511calm
1611calm
1711calm
1811calm
1911calm
2011calm
2111calm
2211calm
2311calm
2411calm
2511calm
2611calm
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 7:35 AM to 7:02 AM, and sunset from 7:03 PM to 7:15 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
111.57:357:03
211.57:347:03
311.57:337:04
411.57:327:04
511.67:317:04
611.67:307:05
711.67:287:05
811.67:277:06
911.77:267:06
1011.77:257:06
1111.77:247:07
1211.77:237:07
1311.87:227:08
1411.87:207:08
1511.87:197:09
1611.87:187:09
1711.97:177:09
1811.97:167:10
1911.97:157:10
2012.07:137:11
2112.07:127:11
2212.07:117:11
2312.07:107:12
2412.17:097:12
2512.17:087:13
2612.17:077:13
2712.17:057:14
2812.27:047:14
2912.27:037:15
3012.27:027:15

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 4.16 kWh/m².

For context, solar energy here swings from a low near 2.77 kWh/m² to a high of 5.66 kWh/m² in December across the year — September's 4.16 kWh/m² falls in the middle.

012345151015202530
Solar energy (kWh/m²)Level
14.3Bright
24.3Bright
34.3Bright
44.3Bright
54.3Bright
64.3Bright
74.3Bright
84.3Bright
94.2Bright
104.2Bright
114.2Bright
124.2Bright
134.2Bright
144.2Bright
154.2Bright
164.2Bright
174.2Bright
184.2Bright
194.2Bright
204.2Bright
214.2Bright
224.2Bright
234.2Bright
244.2Bright
254.1Bright
264.1Bright
274.1Bright
284.2Bright
294.2Bright
304.2Bright
Planning a trip in September

Is September a good time to visit Rio Negro?

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

6.4
Sightseeing
5th-best month of the year
4.5
Beach & pool
8th-best month of the year

September is a reasonable time to visit Rio Negro for sightseeing.

What to pack for Rio Negro in September

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

In September, Rio Negro sees daytime highs around 22°C and nights near 12°C. Worth packing: light clothes and rain gear. About 11 days see rain.

light clothesrain gear

UV index in Rio Negro 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 Negro peaks around January 19 at about 15 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near July 12 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 highExtremeJan 19UV 15Jul 12UV 5
UV index (midday)Level
Jan15Extreme
Feb14Extreme
Mar12Extreme
Apr9Very high
May6High
Jun6High
Jul5High
Aug7High
Sep8Very high
Oct11Extreme
Nov13Extreme
Dec14Extreme

Air quality in Rio Negro 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 Rio Negro is worst in September — around 16 µg/m³ PM2.5 (moderate), about 1.8× the cleanest month (February, 9 µg/m³).

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

01020JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodSep 1115 µg/m³Feb 139 µg/m³
PM2.5 (µg/m³)Level
Jan9Good
Feb9Good
Mar9Good
Apr11Good
May12Moderate
Jun12Good
Jul14Moderate
Aug15Moderate
Sep16Moderate
Oct11Good
Nov10Good
Dec9Good
Location & terrain

Where is Rio Negro?

Rio Negro sits at 26.1°S, 49.8°W, 795 m above sea level, in Brazil. The nearest listed city is Mafra, 1.0 km away.

Topography around Rio Negro

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

Within 3 km, the terrain around Rio Negro has only modest variations in elevation — a maximum elevation change of 110 m around an average of 800 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 196 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,275 m.

The land around Rio Negro is covered by trees (43%) and artificial surfaces (38%) within 3 km, trees (58%) and cropland (30%) within 16 km, and trees (68%) and cropland (23%) within 80 km.

3 km
110 m
16 km
196 m
80 km
1,275 m
treesgrasslandcroplandartificial surfaceswater
September weather nearby: Mafra 1.0 km · Itaiópolis 28 km · Rio Negrinho 32 km · Lapa 38 km · Quitandinha 40 km · São Bento do Sul 45 km · Papanduva 45 km · Três Barras 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 Rio Negro (-26.1058°, -49.7975°, elevation 795 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).