São Mateus do Maranhão weather in September

In September, São Mateus do Maranhão sees average daytime highs of 35°C and overnight lows near 25°C, with 6 mm of rain across 1.1 wet days and about 12 hours of daylight. It is the 2nd-warmest and 11th-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 71% 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 São Mateus do Maranhão's 2nd-clearest and 2nd-windiest month. For the whole year in context, see São Mateus do Maranhão's year-round climate.

Daytime high
35°
2nd warmest
Overnight low
25°
9th coldest
Rainfall
6 mm
1.1 wet days
Daylight
12 hours
5:53 AM – 5:52 PM
Cloud cover
34%
2nd clearest
Wind
10 km/h
2nd windiest
Solar energy
6.3 kWh/m²
Travel score
3.0
out of 10

São Mateus do Maranhão 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 35°C through the month.

A typical September day in São Mateus do Maranhão reaches about 35°C in the afternoon and slips back to 25°C overnight — a 11°C spread between the day's warmth and the night's chill. On most days the high lands between 34°C and 37°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)
13524
23524
33524
43524
53524
63524
73524
83524
93524
103524
113524
123524
133525
143525
153525
163525
173525
183525
193525
203625
213625
223625
233625
243625
253625
263625
273625
283625
293625
303625

How September really feels in São Mateus do Maranhão

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
16 feel dangerously hot (≥ 39°C)
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.

São Mateus do Maranhão weather by month

How September compares with the rest of the year at a glance. September is the 2nd-warmest and 11th-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan32° / 24°24224.312.22.6
Feb31° / 24°2632512.12.5
Mar31° / 24°31228.6122.5
Apr31° / 24°27727.111.92.6
May31° / 24°13419.211.83.4
Jun32° / 23°377.611.84.4
Jul33° / 23°183.611.84.3
Aug34° / 24°51.211.93.7
Sep35° / 25°61.1123.0
Oct36° / 25°133.112.12.6
Nov35° / 25°446.812.22.6
Dec34° / 25°11314.312.22.6

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 71% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 20% of September, with mostly cloudy or overcast conditions the remaining 9%. Skies tend to cloud over as the month goes on.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
1937
2937
3937
4937
5937
6928
7928
8928
9928
10928
11928
12928
13928
14928
15928
16928
17919
18919
199010
209010
219010
229010
239010
249010
258911
268911
278911
288911
298911
308812

Chance of precipitation in September

Any precipitation

São Mateus do Maranhão gets around 6 mm of rain over 1.1 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 4% and peaks near 5% on the wettest days.

0%10%20%30%151015202530
Rain chance (%)
13
23
33
43
53
63
73
83
93
103
113
123
133
143
153
163
173
184
194
204
214
224
234
245
255
265
275
285
295
305

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 58% of days. Sticky, muggy-or-worse air turns up on roughly 97% of them.

0%25%50%75%100%151015202530
Humid (%)Muggy (%)Oppressive (%)
143660
243660
343759
443858
543957
644056
744155
844254
944254
1044353
1144353
1244353
1344353
1444353
1534354
1634255
1734255
1834156
1934156
2024058
2123959
2223860
2323860
2413762
2513762
2613663
2713663
2813663
2913663
3013663

Wind in September

Winds average 10 km/h in September.

Across September, daily wind ranges from about 9 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
19calm
29calm
39calm
49calm
59calm
69calm
79calm
89calm
99calm
109calm
119calm
1210calm
1310calm
1410calm
1510calm
1610calm
1710calm
1810calm
1910calm
2010calm
2110calm
2210calm
2310calm
2410calm
2510calm
2610calm
2710calm
2810calm
2910calm
3010calm

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 6:00 AM to 5:46 AM, and sunset from 5:55 PM to 5:48 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
111.96:005:55
211.95:595:55
311.95:595:55
411.95:595:55
511.95:585:54
611.95:585:54
711.95:575:54
811.95:575:54
912.05:565:53
1012.05:565:53
1112.05:555:53
1212.05:555:53
1312.05:545:52
1412.05:545:52
1512.05:535:52
1612.05:535:52
1712.05:525:51
1812.05:525:51
1912.05:515:51
2012.05:515:51
2112.05:505:50
2212.05:505:50
2312.05:495:50
2412.05:495:50
2512.05:495:49
2612.05:485:49
2712.05:485:49
2812.05:475:49
2912.05:475:48
3012.05:465:48

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 6.3 kWh/m².

For context, solar energy here swings from a low near 4.39 kWh/m² to a high of 6.36 kWh/m² in October across the year — September's 6.3 kWh/m² sits near the top of that range.

0246151015202530
Solar energy (kWh/m²)Level
16.1Intense
26.2Intense
36.2Intense
46.2Intense
56.2Intense
66.2Intense
76.2Intense
86.2Intense
96.2Intense
106.3Intense
116.3Intense
126.3Intense
136.3Intense
146.3Intense
156.3Intense
166.3Intense
176.3Intense
186.3Intense
196.3Intense
206.3Intense
216.3Intense
226.4Intense
236.4Intense
246.4Intense
256.4Intense
266.4Intense
276.4Intense
286.4Intense
296.4Intense
306.4Intense
Planning a trip in September

Hazard calendar for São Mateus do Maranhão

In seasonPeak

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

São Mateus do Maranhão's monsoon runs January–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 São Mateus do Maranhão?

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

3.0
Sightseeing
5th-best month of the year
6.6
Beach & pool
4th-best month of the year

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

What to pack for São Mateus do Maranhão in September

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

In September, São Mateus do Maranhão sees daytime highs around 35°C and nights near 25°C. Pack light clothes and sun protection.

light clothessun protection

UV index in São Mateus do Maranhão 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 São Mateus do Maranhão peaks around March 16 at about 15 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near July 24 at about 10 (very high).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeVery highExtremeMar 16UV 15Jul 24UV 10
UV index (midday)Level
Jan13Extreme
Feb14Extreme
Mar15Extreme
Apr14Extreme
May11Extreme
Jun10Extreme
Jul10Very high
Aug10Very high
Sep12Extreme
Oct12Extreme
Nov11Extreme
Dec11Extreme

Air quality in São Mateus do Maranhão 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 Mateus do Maranhão is worst in October — around 25 µg/m³ PM2.5 (moderate), about 3.0× the cleanest month (June, 8 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateOct 2125 µg/m³Jun 199 µg/m³
PM2.5 (µg/m³)Level
Jan14Moderate
Feb16Moderate
Mar15Moderate
Apr13Moderate
May10Good
Jun8Good
Jul9Good
Aug12Good
Sep16Moderate
Oct25Moderate
Nov23Moderate
Dec17Moderate
Location & terrain

Where is São Mateus do Maranhão?

São Mateus do Maranhão sits at 4.0°S, 44.5°W, 47 m above sea level, in Brazil. The nearest listed city is Alto Alegre do Maranhão, 19 km away.

Topography around São Mateus do Maranhão

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

Within 3 km, the terrain around São Mateus do Maranhão has only modest variations in elevation — a maximum elevation change of 28 m around an average of 42 m above sea level; within 16 km, only modest variations in elevation — a maximum elevation change of 76 m; within 80 km, only modest variations in elevation — a maximum elevation change of 174 m.

The land around São Mateus do Maranhão is covered by grassland (44%) and trees (29%) within 3 km, grassland (50%) and trees (31%) within 16 km, and trees (47%) and grassland (46%) within 80 km.

3 km
28 m
16 km
76 m
80 km
174 m
treesshrubsgrasslandcroplandartificial surfaceswaterwetland
September weather nearby: Alto Alegre do Maranhão 19 km · Bacabal 40 km · Coroatá 40 km · Peritoró 41 km · São Luís Gonzaga do Maranhão 43 km · Pirapemas 45 km · Matões do Norte 46 km · Cantanhede 47 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 Mateus do Maranhão (-4.0417°, -44.475°, elevation 47 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).