Last updated: August 31, 2025
September in Castries, Saint Lucia is characterized by warm tropical temperatures and significant humidity, creating a balmy atmosphere for visitors. With maximum highs reaching 32°C (90°F) and an average temperature of 28°C (83°F), the days are hot and inviting. However, the month also sees an average minimum temperature of 25°C (76°F), offering cooler nights. Rainfall is a notable aspect of September weather, with an average precipitation of 121 mm (4.8 in) over approximately 19 wet days, bringing refreshing showers to the region. The humidity levels hover around 80%, contributing to the tropical feel that defines this vibrant island in the Caribbean.
In September, Castries, Saint Lucia, experiences a warm tropical embrace, with temperatures reflecting a notable rise. The month kicks off with a minimum of 25°C (76°F) and peaks at a steamy 32°C (90°F), making it one of the hottest times of the year. The average temperature sits comfortably at 28°C (83°F), providing the ideal backdrop for beach adventures and island explorations. As the region transitions from the summer heat, September's warmth continues the trend of rising temperatures seen throughout the months, offering sun-soaked days and balmy evenings. Embrace the vibrant atmosphere, but don’t forget your sunscreen—this month’s heat carries the pulse of summer's last hurrah before the cooler months roll in.
In September, Castries, Saint Lucia experiences a notable increase in precipitation, with an average of 121 mm (4.8 in) of rain falling across 19 days. This marks one of the wettest months of the year, continuing the upward trend established in the preceding months of July and August, which saw 105 mm (4.1 in) and 113 mm (4.5 in) respectively. The rainy season peaks in September, often bringing afternoon showers and thunderstorms that refresh the lush landscape. Following September, precipitation slightly increases in October to 128 mm (5.1 in), indicating that the region remains under the influence of tropical weather patterns. Overall, September stands out as a critical month for both rainfall and the vibrant ecosystem of Saint Lucia, setting the stage for the lush tropical environment the island is known for.
In September, humidity levels in Castries, Saint Lucia, settle at a comfortable 80%, maintaining the trend of closely-knit humidity percentages throughout the year. The summer months witness a gradual rise, peaking in July at 84%, before tapering off slightly but consistently. With January and February marking the year’s lowest humidity at 81%, the data reflects a relatively stable climate, where moisture levels hover around the low 80s. The consistency in September's humidity underscores the tropical essence of this Caribbean paradise, making it a prime destination for travelers seeking warm and inviting weather.
In September, Castries, Saint Lucia, experiences an extreme UV Index of 14, maintaining the high levels noted throughout the summer months. This trend reflects a consistent pattern of intense sun exposure that begins in February and stretches all the way through September, where the burn time is critically low at just 10 minutes. Observing the UV Index over the year reveals a striking peak in the early months, specifically from March to August, with slight reductions as October approaches. As visitors and locals bask in the tropical sun during this vibrant time, it's crucial to stay protected; sunglasses, wide-brimmed hats, and ample sunscreen are recommended to ensure safe enjoyment of the beautiful weather. For more details on sun safety in this enchanting locale, you can check the Castries UV Index.
UV Risk Categories
September in Castries, Saint Lucia, offers a delightful blend of sunshine, boasting 319 hours of radiant daylight. As summer fades, the sun continues to grace the island, although slightly less than in the peak months of May and June, which shine brightly with over 350 hours each. This gradual decline marks the transition towards autumn, yet September still stands out with significantly more sunshine than the earlier months of January and February, which linger around 268 and 304 hours respectively. Overall, the sun-soaked days of September invite visitors to enjoy the warm Caribbean breezes while signaling the onset of a scenic fall season.
In Castries, Saint Lucia, September presents a 51% chance of sunny weather, making it one of the more reliable months for sunshine in the latter part of the year. This is a notable peak following the summer months, where the likelihood of sun drifts down to 29% in June and only 46% in both July and August. As the rainy season begins to recede, the prospects of enjoying clear skies increase, aligning with the upward trend observed as the island transitions into the drier months ahead in October and November, which boast 47% and 58% chances of sun, respectively. While early fall may not assure perfect weather, September stands out as a promising option for those seeking warmth and light amidst the tropical charm of Saint Lucia.
In Castries, Saint Lucia, the month of September welcomes a consistent 12 hours of daylight, mirroring the trends seen throughout the summer months. As the year progresses, daylight duration peaks at 12 hours from March through September, creating a sunny atmosphere perfect for exploring the vibrant natural beauty and cultural treasures of the island. Following September, daylight gradually wanes, dropping to 11 hours in October and remaining consistent through December. This rhythm of daylight not only enhances the island's allure but also encourages residents and visitors alike to embrace outdoor activities while basking in the warm Caribbean sun.
In September, the coastal breezes of Castries, Saint Lucia take a noticeable dip, with the average wind speed falling to a gentle 3.9 m/s (9 mph). This marks the lowest point of the year, following a gradual decline from the more vigorous gusts of the summer months, which hover around 6.3 m/s (14 mph) in July. As the island transitions from August's mild winds, where speeds average 5.1 m/s (11 mph), September brings a tranquil reprieve, offering a serene atmosphere perfect for soaking up the tropical sun. However, as autumn approaches, the winds begin to pick up again in October, reflecting a cyclical rhythm that characterizes the island's climate and invites both relaxation and adventure.
Weather in Castries varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Castries, focusing on differences in temperature, rainfall, humidity, and UV levels.
In September, the weather tends to be warmer with temperatures ranging from a minimum of 25°C (76°F) to a maximum of 32°C (90°F) and an average of 28°C (83°F). This month also sees significant precipitation, totaling 121 mm (4.8 in) over 19 days, while the humidity remains high at 80%. In contrast, January experiences slightly cooler temperatures, with a minimum of 22°C (72°F), an average of 26°C (78°F), and a maximum of 30°C (86°F). Additionally, January is much drier, receiving only 36 mm (1.4 in) of rainfall over 15 days, and the humidity remains comparable at 81%. For more detailed information, you can check Castries weather in January.
In comparing the weather between September and February, September tends to be warmer and wetter. The average temperature in September reaches about 28°C (83°F), with maximums climbing up to 32°C (90°F), while February is slightly cooler, averaging 25°C (78°F) at its peak. Additionally, September experiences significantly more rainfall, with a total of 121 mm (4.8 in) over 19 days compared to just 33 mm (1.3 in) over 12 days in February. Both months share high humidity levels at around 80%, but the increased precipitation in September can make it feel more oppressive. For more specific details about the climate in February, you can check Castries weather in February.
In comparing the weather of September and March, September boasts warmer temperatures, with a minimum of 25°C (76°F) and an average of 28°C (83°F), reaching a maximum of 32°C (90°F). In contrast, March features slightly cooler temperatures, with a minimum of 22°C (72°F) and an average of 26°C (79°F), capping at 30°C (85°F). Precipitation levels also differ significantly; September experiences about 121 mm (4.8 in) of rain over 19 days, while March has lighter rainfall, totaling only 38 mm (1.5 in) over 15 days. Both months maintain a consistent humidity level of 80%. For more detailed insights, you can explore Castries weather in March.
In comparing the weather of September to April, we see that September tends to be slightly warmer, with average temperatures reaching around 28°C (83°F), while April has a cooler average of 26°C (80°F). Both months experience high humidity levels, but September's humidity is marginally higher at 80% compared to April's 79%. Additionally, September is significantly wetter, receiving 121 mm (4.8 in) of precipitation over 19 days, whereas April sees only 35 mm (1.4 in) over 14 days. For more detailed information on April weather, you can check Castries weather in April.
In comparing the weather of September and May, September tends to be a bit warmer, with average temperatures reaching 28°C (83°F) compared to May's average of 27°C (81°F). Both months experience similar humidity levels at 80%, but September sees significantly more rainfall, with 121 mm (4.8 in) over 19 days, while May has only 39 mm (1.6 in) across 13 days. This makes May a drier month overall, offering more sunshine and less chance of precipitation. For more detailed insights on May weather, you can visit Castries weather in May.
In comparing the weather between September and June, we see that September boasts slightly higher temperatures, with average highs reaching 32°C (90°F) compared to June’s maximum of 31°C (88°F). However, June features a marginally lower minimum temperature of 24°C (75°F), while both months have similar average temperatures around 27-28°C. September also experiences significantly more rainfall, accumulating 121 mm (4.8 in) over 19 days, compared to June’s 65 mm (2.6 in) over 16 days. Humidity levels remain high in both months, with September at 80% and June a bit higher at 83%. For a detailed look at June weather, check out Castries weather in June.
When comparing the weather in September and July, September tends to be slightly warmer with average temperatures reaching 28°C (83°F), compared to July's average of 27°C (81°F). Both months have similar minimum temperatures, but September boasts a higher maximum at 32°C (90°F) versus July's 31°C (89°F). Precipitation levels in September are also a bit higher, with 121 mm (4.8 in) over 19 days, while July experiences 105 mm (4.1 in) of rain across 24 days. Furthermore, humidity remains elevated in both months, with September at 80% and July at 84%. For a closer look at July's weather specifics, check out Castries weather in July.
Comparing the weather of September and August reveals some interesting similarities and differences. Both months feature warm temperatures, with September having a slightly higher minimum and maximum temperature, peaking at 32°C (90°F) compared to August's 31°C (89°F). The average temperature remains fairly consistent, with September averaging 28°C (83°F) and August at 28°C (82°F). However, September experiences a bit more precipitation, with a total of 121 mm (4.8 in) over 19 days, while August records 113 mm (4.5 in) across 25 days. This indicates that September is slightly wetter but less frequent in rain days compared to August's higher humidity levels, which sit at 81%. For more details on August's weather, you can check Castries weather in August.
In September, the weather features a warm temperature range with a minimum of 25°C (76°F) and an average of 28°C (83°F), reaching a high of 32°C (90°F). The month experiences significant rainfall, totaling 121 mm (4.8 in) over 19 days, alongside high humidity levels at 80%.
In contrast, October maintains a similar warm temperature profile, with a slight decrease in the average temperature to 27°C (81°F) and a minimum of 24°C (76°F), while still reaching up to 32°C (89°F) at times. However, October sees a bit more precipitation at 128 mm (5.1 in) across 21 days and slightly higher humidity at 82%. For more information on the weather specifics in October, you can check the link: Castries weather in October.
In September, the weather is characterized by warm temperatures, with averages around 28°C (83°F) and highs reaching up to 32°C (90°F). The month sees significant rainfall, with 121 mm (4.8 in) recorded over 19 days and a humidity level of 80%. In contrast, November experiences slightly cooler temperatures, averaging 27°C (81°F) and peaking at 31°C (87°F), along with reduced rainfall of 103 mm (4.1 in) across 21 days. The humidity in November is marginally higher at 83%. For more details on what to expect, you can visit Castries weather in November.
September and December showcase notable differences in weather patterns. In September, temperatures are generally warmer, with a minimum of 25°C (76°F) and an average of 28°C (83°F), reaching a maximum of 32°C (90°F). This month also experiences considerably more precipitation, totaling 121 mm (4.8 in) over 19 rainy days, and humidity levels are relatively high at 80%. In contrast, December sees milder temperatures, with a minimum of 22°C (72°F) and an average of 26°C (80°F), peaking at 30°C (86°F). The rainfall decreases significantly to 46 mm (1.8 in) across 16 days, while humidity remains slightly elevated at 82%. For a detailed look at the climate, you can visit Castries weather in December.
September in Castries offers a unique blend of warm temperatures and considerable humidity, distinguishing it from the drier months that precede and follow it. With average highs soaring to a balmy 28°C, and frequent rainfall occurring on 19 days, this month is marked by a vibrant atmosphere that supports lush greenery. While the persistent humidity can make the air feel heavy, it also contributes to the region's rich tropical allure. For a deeper understanding of the seasonal climate patterns, explore our detailed overview at Castries Climate.