São Tomé weather in September

In September, São Tomé sees average daytime highs of 25°C and overnight lows near 24°C, with 46 mm of rain across 7.8 wet days and about 12 hours of daylight. It is the 9th-warmest and 9th-wettest month of the year here.

Day-to-day highs hold fairly steady near 25°C through the month. The sky is clear or mostly clear about 9% of the time in September, and the air most often feels oppressive.

Daylight stretches from about 12 hours at the start of September to 12 hours by month's end. Set against the rest of the year, September is São Tomé's 4th-clearest and 4th-windiest month. For the whole year in context, see São Tomé's year-round climate.

Daytime high
25°
9th warmest
Overnight low
24°
3rd coldest
Rainfall
46 mm
7.8 wet days
Daylight
12 hours
5:27 AM – 5:27 PM
Cloud cover
69%
4th clearest
Wind
20 km/h
4th windiest
Solar energy
5.28 kWh/m²
Travel score
6.9
out of 10

São Tomé is capital city of São Tomé and Príncipe.

Density
3,135/km²
people per km²
Founded
1485

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 25°C through the month.

A typical September day in São Tomé reaches about 25°C in the afternoon and slips back to 24°C overnight — a 1°C spread between the day's warmth and the night's chill. On most days the high lands between 24°C and 26°C. Set against its neighbours, September runs on par with August and on par with October.

20°23°25°28°30°151015202530
Avg high (°C)Avg low (°C)
12524
22524
32524
42524
52524
62524
72524
82524
92524
102524
112524
122524
132524
142524
152524
162524
172524
182524
192524
202524
212524
222524
232525
242525
252525
262525
272525
282525
292525
302525

São Tomé weather by month

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

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan27° / 26°13523.6124.3
Feb28° / 26°11319.3124.6
Mar28° / 26°13320.5124.4
Apr28° / 26°13018.7124.8
May27° / 26°11917125.3
Jun25° / 24°234127.5
Jul24° / 24°82128.0
Aug24° / 24°142.6127.9
Sep25° / 24°467.8126.9
Oct26° / 25°15221.5124.9
Nov26° / 25°21025.7124.1
Dec27° / 25°17426.1124.1

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 9% of the time in September.

Beyond those clear spells, partly cloudy skies cover about 27% of September, with mostly cloudy or overcast conditions the remaining 64%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
13961
23862
33961
43862
53862
63862
73862
83862
93862
103862
113763
123763
133664
143664
153565
163565
173565
183466
193466
203466
213466
223466
233367
243367
253466
263466
273466
283466
293466
303466

Chance of precipitation in September

Any precipitation

São Tomé gets around 46 mm of rain over 7.8 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 27% and peaks near 43% on the wettest days. The odds climb toward the end of the month.

0%10%20%30%40%50%151015202530
Rain chance (%)
112
212
313
414
514
615
716
817
919
1020
1121
1223
1324
1426
1527
1628
1730
1831
1932
2033
2134
2235
2336
2436
2537
2638
2739
2841
2942
3043

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 89% of days. Sticky, muggy-or-worse air turns up on roughly 100% of them.

0%25%50%75%100%151015202530
Muggy (%)Oppressive (%)
13169
22971
32773
42575
52278
62080
71882
81783
91585
101486
111288
121189
131090
14991
15892
16892
17793
18793
19694
20694
21694
22595
23595
24595
25496
26496
27496
28496
29397
30397

Wind in September

Winds average 20 km/h in September.

Across September, daily wind ranges from about 18 km/h on the calmest days to 20 km/h at its breeziest. It stays fairly steady from day to day.

0510152025151015202530
Wind speed (km/h)Feels
120breezy
220breezy
320breezy
420breezy
520breezy
620breezy
720light breeze
820light breeze
920light breeze
1020light breeze
1120light breeze
1220light breeze
1320light breeze
1420light breeze
1520light breeze
1620light breeze
1720light breeze
1820light breeze
1919light breeze
2019light breeze
2119light breeze
2219light breeze
2319light breeze
2419light breeze
2519light breeze
2619light breeze
2719light breeze
2819light breeze
2919light breeze
3018light breeze

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 hours 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 0 minutes over September. Sunrise moves from 5:33 AM to 5:22 AM, and sunset from 5:33 PM to 5:22 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.05:335:33
212.05:325:33
312.05:325:32
412.05:325:32
512.05:315:32
612.05:315:31
712.05:315:31
812.05:305:30
912.05:305:30
1012.05:305:30
1112.05:295:29
1212.05:295:29
1312.05:285:29
1412.05:285:28
1512.05:285:28
1612.05:275:27
1712.05:275:27
1812.05:275:27
1912.05:265:26
2012.05:265:26
2112.05:265:26
2212.05:255:25
2312.05:255:25
2412.05:245:24
2512.05:245:24
2612.05:245:24
2712.05:235:23
2812.05:235:23
2912.05:235:23
3012.05:225:22

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.28 kWh/m².

For context, solar energy here swings from a low near 4.89 kWh/m² to a high of 5.48 kWh/m² in March across the year — September's 5.28 kWh/m² sits near the top of that range.

0246151015202530
Solar energy (kWh/m²)Level
15.4Bright
25.4Bright
35.4Bright
45.4Bright
55.4Bright
65.3Bright
75.3Bright
85.3Bright
95.3Bright
105.3Bright
115.3Bright
125.3Bright
135.3Bright
145.3Bright
155.3Bright
165.2Bright
175.2Bright
185.2Bright
195.2Bright
205.2Bright
215.2Bright
225.2Bright
235.2Bright
245.2Bright
255.2Bright
265.2Bright
275.2Bright
285.2Bright
295.2Bright
305.2Bright
Planning a trip in September

Hazard calendar for São Tomé

In seasonPeak

None of São Tomé'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 Tomé's rainy season runs October–May, 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 São Tomé?

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

6.9
Sightseeing
4th-best month of the year
6.2
Beach & pool
4th-best month of the year

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

What to pack for São Tomé in September

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

In September, São Tomé sees daytime highs around 25°C and nights near 24°C. Worth packing: light clothes and sun protection. About 8 days see rain.

light clothessun protection

Sea temperature near São Tomé in September

The nearest coast averages about 26°C in September — the other half of the beach question. The full-year curve and swim-comfort zones are below.

The sea offshore is warmest in March at about 29°C and coldest in August near 26°C.

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

24°26°28°30°JanFebMarAprMayJunJulAugSepOctNovDecwarmtropicalcomfortable to swim
Sea temperature (°C)Comfort
Jan29Tropical
Feb29Tropical
Mar29Tropical
Apr29Tropical
May28Tropical
Jun27Warm
Jul26Warm
Aug26Warm
Sep26Warm
Oct27Warm
Nov28Warm
Dec28Tropical

UV index in São Tomé 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 Tomé peaks around March 21 at about 14 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near August 12 at about 9 (very high).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecExtremeVery highExtremeMar 21UV 14Aug 12UV 9
UV index (midday)Level
Jan11Extreme
Feb12Extreme
Mar14Extreme
Apr13Extreme
May11Extreme
Jun9Very high
Jul9Very high
Aug8Very high
Sep12Extreme
Oct13Extreme
Nov12Extreme
Dec11Extreme

Air quality in São Tomé 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 Tomé is worst in February — around 24 µg/m³ PM2.5 (moderate), about 4.6× the cleanest month (October, 5 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecModerateGoodModerateGoodModerateFeb 1023 µg/m³Oct 175 µg/m³
PM2.5 (µg/m³)Level
Jan22Moderate
Feb24Moderate
Mar15Moderate
Apr11Good
May12Moderate
Jun16Moderate
Jul17Moderate
Aug13Moderate
Sep8Good
Oct5Good
Nov8Good
Dec15Moderate
Location & terrain

Where is São Tomé?

São Tomé sits at 0.3°N, 6.7°E, 140 m above sea level, in Sao Tome and Principe. The nearest listed city is Port-Gentil, 257 km away.

Topography around São Tomé

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

Within 3 km, the terrain around São Tomé has only modest variations in elevation — a maximum elevation change of 111 m around an average of 23 m above sea level; within 16 km, very significant variations in elevation — a maximum elevation change of 1,396 m; within 80 km, very significant variations in elevation — a maximum elevation change of 1,938 m.

The land around São Tomé is covered by water (43%), trees (31%) and artificial surfaces (24%) within 3 km, water (60%) and trees (36%) within 16 km, and water (90%) within 80 km.

3 km
111 m
16 km
1,396 m
80 km
1,938 m
treesgrasslandartificial surfaceswater
September weather nearby: Port-Gentil 257 km · Akanda 291 km · Libreville 303 km · Owendo 309 km · Ntoum 337 km · Bata 378 km · Lambaréné 407 km · Malabo 443 km

Sao Tome and Principe travel facts

Travel advisory
Level 3
Reconsider Travel
Power plugs
Type C / F
220 V · 50 Hz
Prices
≈ 61% of US
price level, 2025
GDP per capita
$4,084
2025
Safe drinking water
37%
of population, 2024
Homicide rate
3.2
per 100k, 2011
Road deaths
27.9
per 100k/yr, 2019
Income group
Lower middle
World Bank
Religion
Catholic 56%none 21%other 6%Adventist 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 Tomé (0.3376°, 6.7299°, elevation 140 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).