St Lucia weather in September
St Lucia averages 30°C by day and 26°C at night in September, with the sea at 30°C and about 109 mm of rain in the month.
Day
30°C
Night
26°C
Sea
30°C
Rain
109 mm
Flight from London
8½h
What September feels like
September is hot in St Lucia: proper beach weather.
The sea is warm at 30°C: comfortable for long swims.
Expect some rainy spells: about 109 mm falls in the month.
That is 10°C warmer than an average September day in London.
Of the 56 sun destinations we track, St Lucia is the #19 warmest in September.
Going to St Lucia in September?
Share the TikToks and Instagram Reels you've saved for St Lucia to Dream Trip. It finds the places, pins them on a map and builds your days around them.
Want it warmer in September?
These are hotter than St Lucia this month for at most an hour and a half more flying:
St Lucia weather by month
September is highlighted. Compare with August and October, or see the full year in St Lucia.
| Month | Day | Night | Sea | Rain |
|---|---|---|---|---|
| January | 27°C | 24°C | 28°C | 70 mm |
| February | 27°C | 24°C | 27°C | 54 mm |
| March | 28°C | 24°C | 27°C | 55 mm |
| April | 29°C | 25°C | 28°C | 45 mm |
| May | 29°C | 25°C | 28°C | 61 mm |
| June | 29°C | 25°C | 29°C | 107 mm |
| July | 29°C | 25°C | 29°C | 129 mm |
| August | 30°C | 26°C | 30°C | 118 mm |
| September | 30°C | 26°C | 30°C | 109 mm |
| October | 29°C | 26°C | 30°C | 108 mm |
| November | 29°C | 25°C | 29°C | 113 mm |
| December | 28°C | 24°C | 28°C | 71 mm |
St Lucia in September: quick answers
Is St Lucia hot in September?
September is hot in St Lucia: proper beach weather. Average highs are 30°C and lows 26°C.
Can you swim in St Lucia in September?
The sea is warm at 30°C: comfortable for long swims.
Does it rain in St Lucia in September?
Expect some rainy spells: about 109 mm falls in the month.
What is the warmest month in St Lucia?
September, at an average high of 30°C. The coolest is January at 27°C.
How long is the flight to St Lucia from the UK?
About 8½h direct from London, estimated from the 6,769 km distance. Check your airline for exact times.
Still choosing? See where is hot in September for every destination ranked by temperature, sea and flight time.
How we measured this
Averages of every day in September from 2016 to 2025, from the Open-Meteo historical weather archive (ECMWF ERA5 reanalysis). Sea temperature is the 2023 to 2025 average from the Open-Meteo marine archive. Rain is the average monthly total. Reanalysis describes an area about 25 km across, so sheltered resorts can run a degree or two warmer. Flight time is a distance-based estimate from London Heathrow.
Planning St Lucia in September?
Save the restaurants, beaches and views you find on TikTok and Instagram for St Lucia straight to a map, then let Dream Trip turn them into a day-by-day plan.
