Formosa da Serra Negra weather in September

In September, Formosa da Serra Negra sees average daytime highs of 35°C and overnight lows near 23°C, with 12 mm of rain across 1.7 wet days and about 12 hours of daylight. It is the 1st-warmest and 9th-wettest month of the year here.

Day-to-day highs hold fairly steady near 35°C through the month. The sky is clear or mostly clear about 64% of the time in September, and the air most often feels muggy.

Daylight stretches from about 11 h 54 min at the start of September to 12 h 06 min by month's end. Set against the rest of the year, September is Formosa da Serra Negra's 3rd-clearest and 4th-windiest month. For the whole year in context, see Formosa da Serra Negra's year-round climate.

Daytime high
35°
1st warmest
Overnight low
23°
11th coldest
Rainfall
12 mm
1.7 wet days
Daylight
12 hours
6:00 AM – 5:58 PM
Cloud cover
37%
3rd clearest
Wind
9 km/h
4th windiest
Solar energy
6.44 kWh/m²
Travel score
3.4
out of 10

Temperature in September

Average highAverage lowShaded bands: 10–90% of days

Day-to-day highs hold fairly steady near 35°C through the month.

A typical September day in Formosa da Serra Negra reaches about 35°C in the afternoon and slips back to 23°C overnight — a 12°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 on par with August and about 1°C warmer than October.

20°25°30°35°40°151015202530
Avg high (°C)Avg low (°C)
13523
23523
33523
43523
53523
63523
73523
83523
93523
103523
113523
123523
133523
143523
153523
163523
173523
183523
193523
203523
213523
223523
233523
243423
253423
263423
273423
283423
293423
303423

How September really feels in Formosa da Serra Negra

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.

Formosa da Serra Negra weather by month

How September compares with the rest of the year at a glance. September is the 1st-warmest and 9th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan30° / 22°23426.212.33.0
Feb30° / 22°22224.312.22.9
Mar30° / 22°23626.8122.9
Apr31° / 22°15819.711.93.4
May32° / 22°53911.74.3
Jun33° / 22°60.911.64.7
Jul33° / 22°30.411.74.5
Aug34° / 22°10.311.83.8
Sep35° / 23°121.7123.4
Oct33° / 23°498.112.13.5
Nov32° / 23°11215.512.33.6
Dec31° / 22°1632112.43.4

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 64% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 18% of September, with mostly cloudy or overcast conditions the remaining 18%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
18812
28713
38713
48614
58614
68614
78614
88614
98416
108416
118416
128416
138416
148416
158416
168317
178317
188119
198119
208020
218020
228020
237822
247822
257723
267624
277525
287426
297327
307327

Chance of precipitation in September

Any precipitation

Formosa da Serra Negra gets around 12 mm of rain over 1.7 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 6% and peaks near 14% on the wettest days. The odds climb toward the end of the month.

0%10%20%30%151015202530
Rain chance (%)
13
23
33
43
53
63
73
83
93
103
113
123
133
144
154
164
175
185
196
207
217
228
239
2410
2511
2612
2712
2813
2914
3014

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 38% of days. Sticky, muggy-or-worse air turns up on roughly 47% of them.

0%25%50%75%100%151015202530
Dry (%)Comfortable (%)Humid (%)Muggy (%)Oppressive (%)
133139243
233039253
333038264
433037264
533037274
633036284
732936284
832935294
922835304
1022735314
1122635315
1222535325
1322435335
1422335346
1522235356
1622134367
1721934388
1821833398
1921732419
20215314210
21114294411
22112284612
23111274813
24110264914
2519255015
2618235117
2717225218
2816225219
2915215320
3015205321

Wind in September

Winds average 9 km/h in September.

Across September, daily wind ranges from about 8 km/h on the calmest days to 10 km/h at its breeziest. It stays fairly steady from day to day.

051015151015202530
Wind speed (km/h)Feels
110calm
210calm
310calm
410calm
59calm
69calm
79calm
89calm
99calm
109calm
119calm
129calm
139calm
149calm
159calm
169calm
179calm
189calm
199calm
209calm
219calm
229calm
238calm
248calm
258calm
268calm
278calm
288calm
298calm
308calm

Sunrise & sunset in September

DaylightNight

Daylight runs from about 11 h 54 min at the start of September to 12 h 06 min by month's end. The lit band spans sunrise to sunset each day.

Days grow by about 12 minutes over September. Sunrise moves from 6:08 AM to 5:53 AM, and sunset from 6:01 PM to 5:56 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
111.96:086:01
211.96:086:01
311.96:076:00
411.96:076:00
511.96:066:00
611.96:066:00
711.96:056:00
811.96:056:00
911.96:045:59
1011.96:035:59
1111.96:035:59
1211.96:025:59
1311.96:025:59
1412.06:015:58
1512.06:015:58
1612.06:005:58
1712.06:005:58
1812.05:595:58
1912.05:585:57
2012.05:585:57
2112.05:575:57
2212.05:575:57
2312.05:565:57
2412.05:565:57
2512.05:555:56
2612.05:555:56
2712.05:545:56
2812.05:545:56
2912.05:535:56
3012.15:535:56

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 6.44 kWh/m² — the sunniest month for solar.

For context, solar energy here swings from a low near 4.56 kWh/m² to a high of 6.44 kWh/m² in September across the year — September's 6.44 kWh/m² sits near the top of that range.

0246151015202530
Solar energy (kWh/m²)Level
16.4Intense
26.4Intense
36.4Intense
46.4Intense
56.4Intense
66.4Intense
76.5Intense
86.5Intense
96.5Intense
106.5Intense
116.5Intense
126.5Intense
136.5Intense
146.5Intense
156.5Intense
166.5Intense
176.5Intense
186.5Intense
196.5Intense
206.5Intense
216.4Intense
226.4Intense
236.4Intense
246.4Intense
256.4Intense
266.4Intense
276.4Intense
286.3Intense
296.3Intense
306.3Intense
Planning a trip in September

Hazard calendar for Formosa da Serra Negra

In seasonPeak

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

Formosa da Serra Negra's monsoon runs November–April, 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 Formosa da Serra Negra?

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

3.4
Sightseeing
7th-best month of the year
7.0
Beach & pool
4th-best month of the year

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

What to pack for Formosa da Serra Negra in September

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

In September, Formosa da Serra Negra sees daytime highs around 35°C and nights near 23°C. Pack light clothes and sun protection.

light clothessun protection

UV index in Formosa da Serra Negra 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 Formosa da Serra Negra peaks around March 12 at about 15 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near June 22 at about 10 (extreme).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeMar 12UV 15Jun 22UV 10
UV index (midday)Level
Jan14Extreme
Feb15Extreme
Mar15Extreme
Apr14Extreme
May11Extreme
Jun10Very high
Jul10Extreme
Aug11Extreme
Sep12Extreme
Oct12Extreme
Nov12Extreme
Dec10Extreme

Air quality in Formosa da Serra Negra 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 Formosa da Serra Negra is worst in October — around 24 µg/m³ PM2.5 (moderate), about 5.2× the cleanest month (June, 5 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateOct 1524 µg/m³Jun 215 µg/m³
PM2.5 (µg/m³)Level
Jan12Good
Feb11Good
Mar11Good
Apr10Good
May7Good
Jun5Good
Jul5Good
Aug12Good
Sep20Moderate
Oct24Moderate
Nov19Moderate
Dec15Moderate
Location & terrain

Where is Formosa da Serra Negra?

Formosa da Serra Negra sits at 6.4°S, 46.2°W, 340 m above sea level, in Brazil. The nearest listed city is Grajaú, 70 km away.

Topography around Formosa da Serra Negra

How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Formosa da Serra Negra.

Within 3 km, the terrain around Formosa da Serra Negra has only modest variations in elevation — a maximum elevation change of 110 m around an average of 294 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 447 m; within 80 km, significant variations in elevation — a maximum elevation change of 555 m.

The land around Formosa da Serra Negra is covered by trees (45%) and grassland (45%) within 3 km, trees (50%) and grassland (34%) within 16 km, and trees (43%), grassland (33%) and shrubs (21%) within 80 km.

3 km
110 m
16 km
447 m
80 km
555 m
treesshrubsgrasslandcroplandartificial surfaces
September weather nearby: Grajaú 70 km · Sítio Novo 85 km · São Raimundo das Mangabeiras 101 km · Riachão 112 km · Amarante do Maranhão 115 km · Balsas 122 km · Jenipapo dos Vieiras 134 km · Porto Franco 134 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 Formosa da Serra Negra (-6.4446°, -46.1888°, elevation 340 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).