Gustavia weather in September

In September, Gustavia sees average daytime highs of 28°C and overnight lows near 27°C, with 114 mm of rain across 16.8 wet days and about 12.1 hours of daylight. It is the 1st-warmest and 2nd-wettest month of the year here.

Day-to-day highs hold fairly steady near 28°C through the month. The sky is clear or mostly clear about 36% of the time in September, and the air most often feels miserable.

Daylight stretches from about 12 h 24 min at the start of September to 11 h 54 min by month's end. Set against the rest of the year, September is Gustavia's 12th-clearest and 11th-windiest month. For the whole year in context, see Gustavia's year-round climate.

Daytime high
28°
1st warmest
Overnight low
27°
12th coldest
Rainfall
114 mm
16.8 wet days
Daylight
12 h 06 min
6:03 AM – 6:09 PM
Cloud cover
59%
12th clearest
Wind
22 km/h
11th windiest
Solar energy
5.9 kWh/m²
Travel score
5.1
out of 10

Gustavia is main settlement and capital city of St. Barthélemy.

Founded
1785

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 28°C through the month.

A typical September day in Gustavia reaches about 28°C in the afternoon and slips back to 27°C overnight — a 2°C spread between the day's warmth and the night's chill. On most days the high lands between 27°C and 29°C. Set against its neighbours, September runs on par with August and on par with October.

24°26°28°30°32°151015202530
Avg high (°C)Avg low (°C)
12827
22827
32827
42827
52827
62827
72827
82827
92827
102827
112827
122827
132827
142827
152827
162827
172827
182827
192826
202826
212826
222826
232826
242826
252826
262826
272826
282826
292826
302826

How September really feels in Gustavia

Once humidity and wind are folded in, September averages 22 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
22
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.

Gustavia weather by month

How September compares with the rest of the year at a glance. September is the 1st-warmest and 2nd-wettest month here — the current month is highlighted below.

MonthHigh / Low (°C)Rainfall (mm)Wet daysDaylight (hours)Travel score
Jan26° / 24°269.1117.5
Feb25° / 24°206.411.47.8
Mar25° / 24°195.411.98.1
Apr26° / 25°307.412.47.5
May27° / 26°6111.512.86.5
Jun27° / 26°4610.313.16.4
Jul28° / 26°7013.8136.1
Aug28° / 27°841512.65.6
Sep28° / 27°11416.812.15.1
Oct28° / 26°12916.211.65.6
Nov27° / 26°10114.111.26.1
Dec26° / 25°4610.810.97.0

Cloud cover in September

ClearMostly clearPartly cloudyMostly cloudyOvercast

The sky is clear or mostly clear about 36% of the time in September, the cloudiest month of the year.

Beyond those clear spells, partly cloudy skies cover about 14% of September, with mostly cloudy or overcast conditions the remaining 50%.

0%25%50%75%100%151015202530
Clearer (%)Cloudier (%)
15644
25644
35644
45545
55545
65545
75446
85446
95347
105347
115149
125149
135050
144951
154951
164852
174753
184654
194654
204654
214456
224456
234456
244555
254555
264555
274753
284753
294753
304753

Chance of precipitation in September

Any precipitation

Gustavia gets around 114 mm of rain over 16.8 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 55% and peaks near 58% on the wettest days.

0%20%40%60%151015202530
Rain chance (%)
152
253
352
452
552
653
753
853
953
1053
1154
1254
1354
1455
1555
1656
1756
1857
1958
2058
2158
2258
2358
2458
2558
2657
2757
2856
2956
3055

Humidity in September

DryComfortableHumidMuggyOppressiveMiserable

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

By dew point, September lands in the miserable band about 50% of days. Sticky, muggy-or-worse air turns up on roughly 100% of them.

0%25%50%75%100%151015202530
Oppressive (%)Miserable (%)
14357
24357
34357
44357
54357
64357
74357
84357
94456
104456
114555
124555
134654
144753
154753
164852
174951
185050
195149
205248
215347
225446
235545
245644
255743
265842
275941
286040
296139
306238

Wind in September

Winds average 22 km/h in September.

Across September, daily wind ranges from about 21 km/h on the calmest days to 24 km/h at its breeziest. It stays fairly steady from day to day.

0102030151015202530
Wind speed (km/h)Feels
124breezy
223breezy
323breezy
423breezy
523breezy
623breezy
723breezy
823breezy
923breezy
1023breezy
1123breezy
1223breezy
1323breezy
1422breezy
1522breezy
1622breezy
1722breezy
1822breezy
1922breezy
2022breezy
2122breezy
2222breezy
2321breezy
2421breezy
2521breezy
2621breezy
2721breezy
2821breezy
2921breezy
3021breezy

Sunrise & sunset in September

DaylightNight

Daylight runs from about 12 h 24 min at the start of September to 11 h 54 min by month's end. The lit band spans sunrise to sunset each day.

Days shrink by about 30 minutes over September. Sunrise moves from 6:00 AM to 6:05 AM, and sunset from 6:22 PM to 5:56 PM.

12 AM4 AM8 AM12 PM4 PM8 PM12 AM151015202530
Daylight (h)Sunrise (AM)Sunset (PM)
112.46:006:22
212.36:016:21
312.36:016:20
412.36:016:19
512.36:016:18
612.36:016:18
712.36:016:17
812.26:026:16
912.26:026:15
1012.26:026:14
1112.26:026:13
1212.26:026:12
1312.26:026:11
1412.16:026:10
1512.16:036:10
1612.16:036:09
1712.16:036:08
1812.16:036:07
1912.06:036:06
2012.06:036:05
2112.06:036:04
2212.06:046:03
2312.06:046:02
2412.06:046:02
2511.96:046:01
2611.96:046:00
2711.96:045:59
2811.96:055:58
2911.96:055:57
3011.96:055:56

Solar energy in September

Daily solar energy (kWh/m²)

Average shortwave solar energy reaching the ground each day in September, about 5.9 kWh/m².

For context, solar energy here swings from a low near 4.5 kWh/m² to a high of 6.68 kWh/m² in April across the year — September's 5.9 kWh/m² falls in the middle.

0246151015202530
Solar energy (kWh/m²)Level
16.2Intense
26.2Intense
36.2Intense
46.1Intense
56.1Intense
66.1Intense
76.1Intense
86.1Intense
96.0Intense
106.0Intense
116.0Intense
126.0Bright
136.0Bright
145.9Bright
155.9Bright
165.9Bright
175.9Bright
185.8Bright
195.8Bright
205.8Bright
215.8Bright
225.8Bright
235.8Bright
245.7Bright
255.7Bright
265.7Bright
275.7Bright
285.7Bright
295.6Bright
305.6Bright
Planning a trip in September

Hazard calendar for Gustavia

In seasonPeak

In September, Gustavia sits inside its atlantic hurricane and rainy season season. The full year is below, with each hazard's peak months called out.

Gustavia sits in the Atlantic hurricane belt; the season peaks August–October.

Gustavia's rainy season runs July–November, when most of the year's rain falls.

Gustavia sees seasonal dust haze (July), heaviest in July.

Atlantic hurricane
Rainy season
Dust
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec

Is September a good time to visit Gustavia?

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

5.1
Sightseeing
12th-best month of the year
5.8
Beach & pool
12th-best month of the year

September is a reasonable time to visit Gustavia for sightseeing.

What to pack for Gustavia in September

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

In September, Gustavia sees daytime highs around 28°C and nights near 27°C. Pack light clothes and rain gear. Worth having: sun protection and a windbreaker. About 17 days see rain.

light clothesrain gearsun protectiona windbreaker

Sea temperature near Gustavia in September

The nearest coast averages about 29°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 September at about 29°C and coldest in February 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
Jan27Warm
Feb26Warm
Mar26Warm
Apr27Warm
May27Warm
Jun28Warm
Jul28Tropical
Aug29Tropical
Sep29Tropical
Oct29Tropical
Nov28Tropical
Dec27Warm

UV index in Gustavia 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 Gustavia peaks around April 11 at about 13 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 17 at about 7 (high).

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

025710JanFebMarAprMayJunJulAugSepOctNovDecVery highExtremeVery highApr 11UV 13Dec 17UV 7
UV index (midday)Level
Jan8Very high
Feb11Extreme
Mar13Extreme
Apr13Extreme
May12Extreme
Jun12Extreme
Jul12Extreme
Aug11Extreme
Sep12Extreme
Oct10Extreme
Nov8Very high
Dec7High

Air quality in Gustavia 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 Gustavia is worst in July — around 23 µg/m³ PM2.5 (moderate), about 4.1× the cleanest month (December, 6 µg/m³).

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

0102030JanFebMarAprMayJunJulAugSepOctNovDecGoodModerateGoodJul 1223 µg/m³Dec 226 µg/m³
PM2.5 (µg/m³)Level
Jan6Good
Feb8Good
Mar7Good
Apr9Good
May13Moderate
Jun22Moderate
Jul23Moderate
Aug19Moderate
Sep15Moderate
Oct16Moderate
Nov9Good
Dec6Good
Location & terrain

Where is Gustavia?

Gustavia sits at 17.9°N, 62.8°W, 6 m above sea level, in Saint Barthelemy. The nearest listed city is Philipsburg, 25 km away.

Topography around Gustavia

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

Within 3 km, the terrain around Gustavia has only modest variations in elevation — a maximum elevation change of 187 m around an average of 22 m above sea level; within 16 km, significant variations in elevation — a maximum elevation change of 273 m; within 80 km, large variations in elevation — a maximum elevation change of 1,092 m.

The land around Gustavia is covered by water (66%) and trees (20%) within 3 km, water (98%) within 16 km, and water (97%) within 80 km.

3 km
187 m
16 km
273 m
80 km
1,092 m
treesshrubsgrasslandartificial surfacesbare terrainwater
September weather nearby: Philipsburg 25 km · Marigot 31 km · The Valley 42 km · Basseterre 68 km · Codrington 112 km · St. John's 137 km · Brades 140 km · Plymouth 149 km

Saint Barthelemy travel facts

Travel advisory
Level 1
Exercise Normal Precautions

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 Gustavia (17.8962°, -62.8498°, elevation 6 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. Tropical-cyclone seasons are the published climatological basin seasons (NOAA National Hurricane Center / regional warning centres). 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).