Climate and average weather in Castries
In Castries, the weather is muggy, hot, wet, and partly cloudy and remarkably steady, with daytime highs holding near hot levels all year. The wettest stretch peaks around October.
Over the course of the year, the temperature in Castries typically varies from 24°C to 30°C, and is rarely below 23°C or above 31°C. September is the hottest month of the year, while January is the coldest.
Based on the travel score, the best times of year to visit Castries for warm-weather activities are from early January to mid April and early December to late December.
- Hottest
- Sep
- 30°
- Coldest
- Jan
- 24°
- Wettest
- Oct
- 119 mm
- Driest
- Feb
- 21 mm
- Rain / yr
- 775 mm
- 183 wet days
- Daylight
- 11.2–12.8 h
- shortest–longest
- Elevation
- 119 m
- 14.0°N
- Clearest
- Jan
- 38% cloud
Castries is capital of Saint Lucia.
- Density
- 253/km²
- people per km²
- Founded
- 1650
Air quality: WHO Ambient Air Quality Database. Density & description: Wikidata (CC0), GeoNames.
Castries weather by month, at a glance
The whole year in one picture — sky, rain, humidity, temperature and travel score. Click any band to jump to its full chart.
Each stripe is one measure across the whole year, stacked so a single day reads top to bottom. The sky band runs overcast grey on top down to clear blue at the base — more blue means sunnier — followed by the rainfall curve, the humidity band, a temperature strip that tints each stretch of the year by how warm its average high is, and the travel-score line at the foot. Scan straight down any date to read that day across every measure at once; the score climbs highest around early January to mid April.
Temperature through the year
Daily average highs and lows in Castries, from 1991–2020 of climate data. The shaded bands show the range most days fall in — 10th to 90th percentile.
Temperatures in Castries stay fairly even through the year, without a distinct hot or cool season. The warmest month is September, with an average high of 30°C and low of 26°C; the coolest is January, with an average low of 24°C and high of 28°C.
Days typically run about 4°C warmer than nights year-round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high (°C) | 28 | 28 | 28 | 29 | 29 | 29 | 29 | 30 | 30 | 29 | 29 | 28 |
| Avg low (°C) | 24 | 24 | 24 | 25 | 25 | 25 | 25 | 26 | 26 | 25 | 25 | 25 |
| Avg high (°C) | Avg low (°C) | |
|---|---|---|
| Jan | 28 | 24 |
| Feb | 28 | 24 |
| Mar | 28 | 24 |
| Apr | 29 | 25 |
| May | 29 | 25 |
| Jun | 29 | 25 |
| Jul | 29 | 25 |
| Aug | 30 | 26 |
| Sep | 30 | 26 |
| Oct | 29 | 25 |
| Nov | 29 | 25 |
| Dec | 28 | 25 |
How hot and cold Castries really feels
The felt-temperature range through the year — heat index on the day's high (summer humidity), wind chill on the night's low (winter wind). The dashed lines are the plain thermometer; the gap is how much hotter or colder it really feels.
On the hottest afternoons, once humidity is folded in, Castries feels like about 34°C (around September 9). About 193 days a year carry some heat stress, peaking in September.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Feels-like high (°C) | 30 | 29 | 30 | 31 | 33 | 33 | 33 | 34 | 34 | 33 | 32 | 31 |
| Air high (°C) | 28 | 28 | 28 | 29 | 29 | 29 | 29 | 30 | 30 | 29 | 29 | 28 |
| Feels-like low (°C) | 24 | 24 | 24 | 24 | 25 | 25 | 25 | 25 | 26 | 25 | 25 | 24 |
| Air low (°C) | 24 | 24 | 24 | 25 | 25 | 25 | 25 | 26 | 26 | 25 | 25 | 25 |
| Feels-like high (°C) | Air high (°C) | Feels-like low (°C) | Air low (°C) | |
|---|---|---|---|---|
| Jan | 30 | 28 | 24 | 24 |
| Feb | 29 | 28 | 24 | 24 |
| Mar | 30 | 28 | 24 | 24 |
| Apr | 31 | 29 | 24 | 25 |
| May | 33 | 29 | 25 | 25 |
| Jun | 33 | 29 | 25 | 25 |
| Jul | 33 | 29 | 25 | 25 |
| Aug | 34 | 30 | 25 | 26 |
| Sep | 34 | 30 | 26 | 26 |
| Oct | 33 | 29 | 25 | 25 |
| Nov | 32 | 29 | 25 | 25 |
| Dec | 31 | 28 | 24 | 25 |
Average hourly temperature in Castries
A compact picture of the whole year, hour by hour: each column is a day, each row an hour, and the color is the modeled average temperature. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
Read left to right for the day of the year and top to bottom for the hour of the day; the color is the modeled temperature, cool blues through to hot reds on the same scale as the other charts. A vertical slice is a single day's swing — coolest just before dawn, warmest in the mid-afternoon — while a horizontal slice follows one hour across the seasons. The darker overlay marks night and the lighter one the twilight around sunrise and sunset. Colors run warmest on September afternoons, near 30°C, and coldest before dawn in January, near 24°C.
Castries weather by month
Every month at a glance. Click a month for its detailed page.
| Month | High / Low (°C) | Rainfall (mm) | Wet days | Daylight (hours) | Travel score |
|---|---|---|---|---|---|
| Jan | 28° / 24° | 31 | 11.8 | 11.3 | 6.5 |
| Feb | 28° / 24° | 21 | 8.8 | 11.5 | 6.7 |
| Mar | 28° / 24° | 26 | 9.8 | 11.9 | 6.1 |
| Apr | 29° / 25° | 36 | 11.5 | 12.3 | 5.4 |
| May | 29° / 25° | 47 | 12.5 | 12.6 | 4.9 |
| Jun | 29° / 25° | 65 | 15.1 | 12.8 | 4.5 |
| Jul | 29° / 25° | 83 | 20.3 | 12.7 | 4.2 |
| Aug | 30° / 26° | 99 | 20.7 | 12.5 | 4.0 |
| Sep | 30° / 26° | 104 | 19.4 | 12.1 | 3.9 |
| Oct | 29° / 25° | 119 | 20.9 | 11.7 | 4.0 |
| Nov | 29° / 25° | 102 | 18.9 | 11.4 | 4.5 |
| Dec | 28° / 25° | 42 | 13 | 11.2 | 5.7 |
Chance of rain
How likely it is to rain on a typical day, and how that shifts across the wetter and drier seasons.
Castries gets about 775 mm of precipitation a year. On a typical day the chance of rain is very wet, but that rises and falls sharply with the seasons.
The wetter season lasts 5.8 months, from around Jun 9 to Dec 1, peaking in August at about 70% chance on a given day. The drier stretch runs the rest of the year, bottoming out around Mar 9.
October is the wettest month by volume, with 119 mm over about 21 wet days; February is the driest, with 21 mm.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rain on a day (%) | 38 | 32 | 32 | 37 | 41 | 52 | 64 | 68 | 64 | 67 | 62 | 43 |
| Rain days | 12 | 9 | 10 | 12 | 13 | 15 | 20 | 21 | 19 | 21 | 19 | 13 |
| Rain on a day (%) | Rain days | |
|---|---|---|
| Jan | 38 | 12 |
| Feb | 32 | 9 |
| Mar | 32 | 10 |
| Apr | 37 | 12 |
| May | 41 | 13 |
| Jun | 52 | 15 |
| Jul | 64 | 20 |
| Aug | 68 | 21 |
| Sep | 64 | 19 |
| Oct | 67 | 21 |
| Nov | 62 | 19 |
| Dec | 43 | 13 |
Monthly rainfall
Over a full year, Castries collects about 775 mm of rain across 183 wet days — roughly 65 mm in an average month.
It doesn’t fall evenly. October is the wettest month with 119 mm, while February is the driest at just 21 mm. The three wettest months alone bring about 42% of the year’s total.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Rainfall (mm) | 31 | 21 | 26 | 36 | 47 | 65 | 83 | 99 | 104 | 119 | 102 | 42 |
| Rain days | 12 | 9 | 10 | 12 | 13 | 15 | 20 | 21 | 19 | 21 | 19 | 13 |
| Rainfall (mm) | Rain days | |
|---|---|---|
| Jan | 31 | 12 |
| Feb | 21 | 9 |
| Mar | 26 | 10 |
| Apr | 36 | 12 |
| May | 47 | 13 |
| Jun | 65 | 15 |
| Jul | 83 | 20 |
| Aug | 99 | 21 |
| Sep | 104 | 19 |
| Oct | 119 | 21 |
| Nov | 102 | 19 |
| Dec | 42 | 13 |
Clouds and sunshine
How often the daytime sky is clear, partly cloudy or overcast.
In Castries, the average share of the sky covered by clouds shows significant seasonal variation over the course of the year.
The clearer part of the year begins around November 21 and lasts for 4.5 months, ending around April 5. The clearest month is January, when the sky is clear, mostly clear, or partly cloudy 87% of the time on average.
The cloudier part of the year begins around July 27 and lasts for 3.8 months, ending around November 20. The cloudiest month is September, when it is overcast or mostly cloudy 55% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Clearer (%) | 87 | 84 | 74 | 58 | 52 | 45 | 59 | 58 | 45 | 45 | 59 | 76 |
| Cloudier (%) | 13 | 16 | 26 | 42 | 48 | 55 | 41 | 42 | 55 | 55 | 41 | 24 |
| Clearer (%) | Cloudier (%) | |
|---|---|---|
| Jan | 87 | 13 |
| Feb | 84 | 16 |
| Mar | 74 | 26 |
| Apr | 58 | 42 |
| May | 52 | 48 |
| Jun | 45 | 55 |
| Jul | 59 | 41 |
| Aug | 58 | 42 |
| Sep | 45 | 55 |
| Oct | 45 | 55 |
| Nov | 59 | 41 |
| Dec | 76 | 24 |
Daylight, sunrise and sunset
Hours of daylight through the year, with sunrise and sunset times.
The gold band is daylight — sunrise runs along its lower edge, sunset along the upper — so it widens toward summer and pinches toward winter, with night the dark area above and below. The longest day, around May 30, brings about 12 h 48 min of light; the shortest, around January 1, only 11 h 12 min — a swing of roughly 1 h 36 min.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Daylight (h) | 11.3 | 11.5 | 11.9 | 12.3 | 12.6 | 12.8 | 12.7 | 12.5 | 12.1 | 11.7 | 11.4 | 11.2 |
| Sunrise (AM) | 6:36 | 6:33 | 6:17 | 5:55 | 5:41 | 5:40 | 5:47 | 5:54 | 5:56 | 5:59 | 6:09 | 6:25 |
| Sunset (PM) | 5:51 | 6:05 | 6:11 | 6:14 | 6:20 | 6:29 | 6:32 | 6:22 | 6:01 | 5:39 | 5:29 | 5:36 |
| Daylight (h) | Sunrise (AM) | Sunset (PM) | |
|---|---|---|---|
| Jan | 11.3 | 6:36 | 5:51 |
| Feb | 11.5 | 6:33 | 6:05 |
| Mar | 11.9 | 6:17 | 6:11 |
| Apr | 12.3 | 5:55 | 6:14 |
| May | 12.6 | 5:41 | 6:20 |
| Jun | 12.8 | 5:40 | 6:29 |
| Jul | 12.7 | 5:47 | 6:32 |
| Aug | 12.5 | 5:54 | 6:22 |
| Sep | 12.1 | 5:56 | 6:01 |
| Oct | 11.7 | 5:59 | 5:39 |
| Nov | 11.4 | 6:09 | 5:29 |
| Dec | 11.2 | 6:25 | 5:36 |
Sunny days
How many genuinely sunny days each month brings — days the sky stays clear or mostly clear — banded into plain-language zones.
Castries averages about 12 sunny days a month — counting the days the sky stays clear or mostly clear — with a clear seasonal swing between 7 and 20 days.
The sunnier stretch runs 4.2 months, from around Nov 21 to Mar 27. The sunniest month is January, with roughly 19 sunny days (bright).
The greyest month is October, down near 8 sunny days — about 57% fewer than the January peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sunny days | 20 | 17 | 14 | 10 | 9 | 8 | 12 | 12 | 9 | 9 | 11 | 17 |
| Sky | Bright | Bright | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Mixed | Bright |
| Sunny days | Sky | |
|---|---|---|
| Jan | 20 | Bright |
| Feb | 17 | Bright |
| Mar | 14 | Mixed |
| Apr | 10 | Mixed |
| May | 9 | Mixed |
| Jun | 8 | Mixed |
| Jul | 12 | Mixed |
| Aug | 12 | Mixed |
| Sep | 9 | Mixed |
| Oct | 9 | Mixed |
| Nov | 11 | Mixed |
| Dec | 17 | Bright |
Humidity comfort
Share of days at each humidity comfort level, based on the dew point — the measure that tracks how muggy it actually feels.
Humidity comfort is graded by the dew point — the temperature at which the air would be fully saturated — because it tracks how muggy it actually feels far better than relative humidity does. A low dew point feels dry and crisp; a high one feels sticky and oppressive no matter the reading on a humidity gauge.
Castries is humid all year round — on a typical day the air feels at least humid, and there is no real dry season to wait for.
The stickiest month is January, when it feels muggy, oppressive or miserable about 94% of the time. Even in April, the mildest month, the air is dry or comfortable only 0% of the time.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Humid (%) | 6 | 10 | 9 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 2 |
| Muggy (%) | 66 | 80 | 73 | 49 | 21 | 5 | 1 | 0 | 1 | 1 | 5 | 35 |
| Oppressive (%) | 28 | 10 | 18 | 49 | 78 | 91 | 94 | 88 | 85 | 88 | 91 | 63 |
| Miserable (%) | 0 | 0 | 0 | 0 | 2 | 4 | 5 | 12 | 15 | 11 | 3 | 0 |
| Humid (%) | Muggy (%) | Oppressive (%) | Miserable (%) | |
|---|---|---|---|---|
| Jan | 6 | 66 | 28 | 0 |
| Feb | 10 | 80 | 10 | 0 |
| Mar | 9 | 73 | 18 | 0 |
| Apr | 1 | 49 | 49 | 0 |
| May | 0 | 21 | 78 | 2 |
| Jun | 0 | 5 | 91 | 4 |
| Jul | 0 | 1 | 94 | 5 |
| Aug | 0 | 0 | 88 | 12 |
| Sep | 0 | 1 | 85 | 15 |
| Oct | 0 | 1 | 88 | 11 |
| Nov | 0 | 5 | 91 | 3 |
| Dec | 2 | 35 | 63 | 0 |
Wind
Average wind speed through the year, banded into plain-language speed zones so a number reads as 'breezy' or 'calm' without knowing the scale.
This is the average sustained wind speed at the standard 10 metres above open ground — the steady flow a weather station reports, not the sharper gusts that come and go, which can run half again as fast. It's the number that says whether a place is generally breezy or calm.
Across the year, average wind speed in Castries is typically light breeze, near 20 km/h, and varies moderately with the seasons.
The windier part of the year lasts 7.7 months, from around Dec 8 to Jul 29. The windiest month is June, averaging about 22 km/h (breezy).
The calmer part of the year runs from around Jul 30 to Dec 7, with September the calmest month at about 16 km/h.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Wind speed (km/h) | 22 | 22 | 21 | 20 | 21 | 22 | 21 | 18 | 16 | 16 | 18 | 21 |
| Feels | breezy | breezy | breezy | breezy | breezy | breezy | breezy | light breeze | light breeze | light breeze | light breeze | breezy |
| Wind speed (km/h) | Feels | |
|---|---|---|
| Jan | 22 | breezy |
| Feb | 22 | breezy |
| Mar | 21 | breezy |
| Apr | 20 | breezy |
| May | 21 | breezy |
| Jun | 22 | breezy |
| Jul | 21 | breezy |
| Aug | 18 | light breeze |
| Sep | 16 | light breeze |
| Oct | 16 | light breeze |
| Nov | 18 | light breeze |
| Dec | 21 | breezy |
Hazard calendar for Castries
When the seasonal hazards worth planning around — the rainy season, tropical-cyclone risk and dust haze — are active through the year.
Castries sits in the Atlantic hurricane belt; the season peaks August–October.
Castries's rainy season runs June–November, when most of the year's rain falls.
Castries sees seasonal dust haze (June–July), heaviest in June.
Best time to visit Castries
To characterize how pleasant the weather is in Castries throughout the year, we compute two travel scores — one for general sightseeing, one for beach and pool weather.
Around early April, Castries is still near the tail of its best-weather window — great conditions with the peak-season crowds already thinning.
Inferred from the travel-score curve; month-by-month visitor numbers are a planned addition.
The travel score favors clear, rainless days with daytime highs between 18°C and 28°C. Based on this score, the best time of year to visit Castries for general outdoor tourist activities is from early December to mid April, with a peak score in the last week of January.
The travel score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Travel score (0–10) | 6.5 | 6.7 | 6.1 | 5.4 | 4.9 | 4.5 | 4.2 | 4.0 | 3.9 | 4.0 | 4.6 | 5.7 |
| Rating | good | good | good | fair | fair | fair | fair | fair | fair | fair | fair | good |
| Travel score (0–10) | Rating | |
|---|---|---|
| Jan | 6.5 | good |
| Feb | 6.7 | good |
| Mar | 6.1 | good |
| Apr | 5.4 | fair |
| May | 4.9 | fair |
| Jun | 4.5 | fair |
| Jul | 4.2 | fair |
| Aug | 4.0 | fair |
| Sep | 3.9 | fair |
| Oct | 4.0 | fair |
| Nov | 4.6 | fair |
| Dec | 5.7 | good |
The beach/pool score favors clear, rainless days with daytime highs between 24°C and 34°C. Based on this score, the best time of year to visit Castries for hot-weather activities is from late November to early July, with a peak score in the first week of February.
The beach/pool score (filled area), and its constituents: the temperature score (red line), the cloud cover score (blue line), and the precipitation score (green line).
What to pack for Castries, by month
Month by month, what's worth putting in the bag — from the temperature range, rain chance, sun and wind. Tap a month for a quick packing note.
Castries packs about the same all year — highs hold near 30°C. Across the year the things worth having are light clothes, rain gear, sun protection and a windbreaker.
In September, Castries sees daytime highs around 30°C and nights near 26°C. Pack light clothes and rain gear. Worth having: sun protection. About 19 days see rain.
Sea temperature near Castries
Average ocean temperature at the nearest coast, month by month, banded into swim-comfort zones — the other half of the beach question.
The sea at the nearest coast (about 19 km away) is warmest in September at about 29°C and coldest in February near 27°C.
The water stays above 20°C all year — warm enough for a swim any month.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Sea temperature (°C) | 27 | 27 | 27 | 27 | 28 | 28 | 28 | 29 | 29 | 29 | 29 | 28 |
| Comfort | Warm | Warm | Warm | Warm | Warm | Warm | Tropical | Tropical | Tropical | Tropical | Tropical | Warm |
| Sea temperature (°C) | Comfort | |
|---|---|---|
| Jan | 27 | Warm |
| Feb | 27 | Warm |
| Mar | 27 | Warm |
| Apr | 27 | Warm |
| May | 28 | Warm |
| Jun | 28 | Warm |
| Jul | 28 | Tropical |
| Aug | 29 | Tropical |
| Sep | 29 | Tropical |
| Oct | 29 | Tropical |
| Nov | 29 | Tropical |
| Dec | 28 | Warm |
UV index (midday) in Castries by month
Clear-sky midday UV index through the year, shaded by the WHO exposure levels — how much sun protection each month calls for.
Under clear skies, the midday UV index in Castries peaks around March 21 at about 14 (extreme) — sunscreen, a hat and midday shade are essential. It bottoms out near December 13 at about 8 (very high).
The index reaches 3 or more — the level where the WHO recommends sun protection — every month of the year.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV index (midday) | 9 | 12 | 14 | 13 | 12 | 11 | 12 | 11 | 12 | 11 | 9 | 8 |
| Level | Very high | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Extreme | Very high | Very high |
| UV index (midday) | Level | |
|---|---|---|
| Jan | 9 | Very high |
| Feb | 12 | Extreme |
| Mar | 14 | Extreme |
| Apr | 13 | Extreme |
| May | 12 | Extreme |
| Jun | 11 | Extreme |
| Jul | 12 | Extreme |
| Aug | 11 | Extreme |
| Sep | 12 | Extreme |
| Oct | 11 | Extreme |
| Nov | 9 | Very high |
| Dec | 8 | Very high |
Average hourly UV index in Castries
Modeled clear-sky UV for every hour of every day — when in the day sun protection actually matters.
The whole year hour by hour: each column is a day, each row an hour, and the color is the modeled clear-sky UV index — the midday peak scaled down as the sun sits lower in the sky. Darker overlays mark night, lighter ones the civil-twilight hours around sunrise and sunset.
UV falls off far faster than brightness as the sun drops, so even in March the burn window is concentrated in the middle of the day: about 8 hours a day reach index 3 (protection recommended), and 6.5 hours reach 6 or more. Mornings and late afternoons stay comparatively gentle year round.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| UV ≥ 3 (h/day) | 7 | 7.5 | 8 | 8 | 8.5 | 8 | 8 | 8 | 8 | 7.5 | 6.5 | 6.5 |
| UV ≥ 6 (h/day) | 4.5 | 5.5 | 6.5 | 6.5 | 6.5 | 6 | 6 | 5.5 | 6 | 5.5 | 4 | 4 |
| UV ≥ 3 (h/day) | UV ≥ 6 (h/day) | |
|---|---|---|
| Jan | 7 | 4.5 |
| Feb | 7.5 | 5.5 |
| Mar | 8 | 6.5 |
| Apr | 8 | 6.5 |
| May | 8.5 | 6.5 |
| Jun | 8 | 6 |
| Jul | 8 | 6 |
| Aug | 8 | 5.5 |
| Sep | 8 | 6 |
| Oct | 7.5 | 5.5 |
| Nov | 6.5 | 4 |
| Dec | 6.5 | 4 |
Air quality in Castries by month
Average fine-particle pollution (PM2.5) through the year — so you can see which months the air is worst, not just the yearly average.
Air quality in Castries is worst in June — around 29 µg/m³ PM2.5 (moderate), about 2.9× the cleanest month (December, 10 µg/m³).
Modeled monthly averages (CAMS reanalysis, 2015–2024).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| PM2.5 (µg/m³) | 10 | 14 | 12 | 16 | 19 | 29 | 25 | 21 | 15 | 18 | 13 | 10 |
| Level | Good | Moderate | Good | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Moderate | Good |
| PM2.5 (µg/m³) | Level | |
|---|---|---|
| Jan | 10 | Good |
| Feb | 14 | Moderate |
| Mar | 12 | Good |
| Apr | 16 | Moderate |
| May | 19 | Moderate |
| Jun | 29 | Moderate |
| Jul | 25 | Moderate |
| Aug | 21 | Moderate |
| Sep | 15 | Moderate |
| Oct | 18 | Moderate |
| Nov | 13 | Moderate |
| Dec | 10 | Good |
Growing season
Castries is frost-free year round — even the coldest nights rarely reach freezing, so there is no start or end to the growing season.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Frost-free chance (%) | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 | 100 |
| Frost nights | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Frost-free chance (%) | Frost nights | |
|---|---|---|
| Jan | 100 | 0 |
| Feb | 100 | 0 |
| Mar | 100 | 0 |
| Apr | 100 | 0 |
| May | 100 | 0 |
| Jun | 100 | 0 |
| Jul | 100 | 0 |
| Aug | 100 | 0 |
| Sep | 100 | 0 |
| Oct | 100 | 0 |
| Nov | 100 | 0 |
| Dec | 100 | 0 |
Growing degree days
Growing degree days tally heat above 10°C: each day adds however many degrees its average temperature runs over that threshold, and cold days add nothing. Castries banks about 6,155 degree days a year, and the running total — which growers use to time plantings and predict maturity — climbs fastest around September.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Growing degree days (°C·days) | 491 | 442 | 498 | 499 | 537 | 523 | 539 | 544 | 531 | 539 | 505 | 508 |
| Growing degree days (°C·days) | |
|---|---|
| Jan | 491 |
| Feb | 442 |
| Mar | 498 |
| Apr | 499 |
| May | 537 |
| Jun | 523 |
| Jul | 539 |
| Aug | 544 |
| Sep | 531 |
| Oct | 539 |
| Nov | 505 |
| Dec | 508 |
Solar energy
Average daily shortwave solar energy reaching the ground, banded into brightness zones so the number means something at a glance.
Solar energy is how much sunlight actually reaches the ground each day, measured in kilowatt-hours per square metre (kWh/m²) — the combined effect of how long the sun is up, how high it climbs, and how much cloud gets in the way. It's the raw fuel a solar panel has to work with: for scale, 1 kWh/m² a day is dim and wintry, while 7+ is desert-bright.
Castries receives about 5.9 kWh/m² a day of solar energy on average — bright — with a clear seasonal swing between 4.9 and 6.7 kWh/m².
The brighter stretch of the year lasts 7.0 months, from around Feb 18 to Sep 17. The brightest month is April, averaging about 6.6 kWh/m² (intense).
The dimmest month is December, down near 4.9 kWh/m² — roughly 25% less than the April peak.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Solar energy (kWh/m²) | 5.2 | 5.8 | 6.4 | 6.7 | 6.6 | 6.4 | 6.3 | 6.2 | 6.0 | 5.5 | 5.0 | 5.0 |
| Level | Bright | Bright | Intense | Intense | Intense | Intense | Intense | Intense | Bright | Bright | Bright | Bright |
| Solar energy (kWh/m²) | Level | |
|---|---|---|
| Jan | 5.2 | Bright |
| Feb | 5.8 | Bright |
| Mar | 6.4 | Intense |
| Apr | 6.7 | Intense |
| May | 6.6 | Intense |
| Jun | 6.4 | Intense |
| Jul | 6.3 | Intense |
| Aug | 6.2 | Intense |
| Sep | 6.0 | Bright |
| Oct | 5.5 | Bright |
| Nov | 5.0 | Bright |
| Dec | 5.0 | Bright |
Where is Castries?
Castries sits at 14.0°N, 61.0°W, 119 m above sea level, in Saint Lucia. The nearest listed city is Gros Islet, 10 km away.
What Castries looks like
Topography around Castries
How much the land rises and falls, and what covers it, within 3, 16 and 80 km of Castries.
Within 3 km, the terrain around Castries has significant variations in elevation — a maximum elevation change of 266 m around an average of 45 m above sea level; within 16 km, large variations in elevation — a maximum elevation change of 900 m; within 80 km, large variations in elevation — a maximum elevation change of 1,191 m.
The land around Castries is covered by trees (46%) and water (35%) within 3 km, water (55%) and trees (42%) within 16 km, and water (89%) within 80 km.
Saint Lucia travel facts
- Travel advisory
- Level 2
- Exercise Increased Caution
- Power plugs
- Type A / B / G
- 240 V · 50 Hz
- Prices
- ≈ 51% of US
- price level, 2025
- GDP per capita
- $14,746
- 2025
- Homicide rate
- 39
- per 100k, 2023
- Road deaths
- 29.8
- per 100k/yr, 2019
- Income group
- Upper middle
- World Bank
- Religion
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 Castries (13.9957°, -61.0061°, elevation 119 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).