Saint Lucia (Castries) weather in September
Temperature, sea and sunshine in September: long-term averages from 30 years of weather data, not a forecast.
Holiday weather in September
Good
Best time to visit: December – July
What is the weather like in Saint Lucia (Castries) in September?
In September, Saint Lucia (Castries) is hot: daytime highs average 29 °C, and even at night it stays warm at around 25 °C. The sea averages 29.3 °C – almost as warm as a bath. The sun shines for around 8 hours a day. It is the rainy season: rain falls on about 20 days, totalling 102 mm. On about 7 days the thermometer climbs to 30 °C or more. The air is often humid and muggy. All in all, September is a good month for a holiday in Saint Lucia (Castries).
September compared
How the weather changes from August to October. Tap a month to open it.
| AugustAug | SeptemberSep | OctoberOct | |
|---|---|---|---|
| Score | 79 | 76 | 76 |
| Day | 29° | 29° | 29° |
| Night | 25° | 25° | 25° |
| Sea | 29° | 29° | 29° |
| Sun | 9 h | 8 h | 8 h |
| Rain days | 22 | 20 | 22 |
More details for September
- Daylight
- 12 h 14 min05:53 – 18:06
- UV index
- 13 · extremeclear sky, noon (estimate)All months
- Muggy days
- 30 daysdew point 18 °C or moreAll months
- Wind
- 19 km/haverage daily peakAll months
- Cloud cover
- 61 %on averageAll months
- Hot days
- 7 days30 °C or moreAll months
- Time zone
- UTC−4America/St_Lucia
How the score comes together
- Temperatureweight 35 %100 %
- Seaweight 25 %100 %
- Sunshineweight 20 %78 %
- Few rainy daysweight 20 %0 %
Each factor is rated from 0 to 100 % and weighted for the travel style “Sun, sea & sand”.
What to pack in September
- Swimwear
- Sunscreen
- Sunglasses & sun hat
- Light, breathable clothes
- Insect repellent
- Rain jacket or umbrella
Saint Lucia (Castries) in September: quick answers
Is Saint Lucia (Castries) hot in September?
Yes. In September, Saint Lucia (Castries) is hot: daytime highs average 29 °C and nights stay around 25 °C. On about 7 days the thermometer climbs to 30 °C or more.
Can you swim in Saint Lucia (Castries) in September?
Yes. In September the sea averages 29.3 °C – almost as warm as a bath.
Does it rain much in Saint Lucia (Castries) in September?
It rains often – on about 20 days, adding up to 102 mm.
Saint Lucia (Castries) month by month
The whole year in Saint Lucia (Castries)All destinations: Saint LuciaCaribbean weather in SeptemberWhere to go in SeptemberSea temperature in September
Climate averages 1996–2025, not a forecast. Data: Copernicus ERA5 / ERA5-Land via Open-Meteo.com (CC BY 4.0), NOAA OISST, WMO 1991–2020 (NOAA NCEI), GeoNames (CC BY 4.0). Sources & licences