Seychelles Weather in September — Temperature, Sea Conditions & Yacht Travel Guide
May 21, 2026
September in Seychelles brings average daytime temperatures of 84°F (29°C) and nighttime lows of 77°F (25°C), with sea temperatures holding steady around 81°F (27°C). Monthly rainfall totals 90–110 mm spread across 8–10 rainy days, while the southeast trade winds blow at an average of 11–13 mph (18–21 km/h) and weaken gradually through the month. Daylight lasts approximately 12 hours, with sunrise near 6:10 AM and sunset around 6:15 PM. The month marks the closing phase of the southeast monsoon and the start of the transition toward the calmer inter-monsoon period.
September Climate Overview in Seychelles
September is the final month of the southeast monsoon season in Seychelles, transitioning toward the calm inter-monsoon period that begins in October. The month is warm and moderately humid, with steadily decreasing cloud cover as the trade winds lose strength.
The dominant weather pattern in September is the southeast trade wind, which moves cooler air across the islands and produces moderate sea conditions along east-facing coastlines. Cloud cover drops from around 57% at the start of the month to 52% by the end, indicating a gradual return of clearer skies.
September differs from the peak rainy months of December and January in two ways. Rainfall totals are roughly one-third of the December figure, and the rains in September fall as short afternoon showers rather than sustained tropical downpours. Daytime temperatures sit several degrees below the April peak and 1–2°F above the August minimum.
Comfort levels in September are high for outdoor activities. Temperatures stay within a narrow range, the sea remains warm for swimming, and the trade wind keeps daytime heat manageable on most beaches.
Air Temperature in Seychelles in September
Daily high temperatures in September average 84°F (29°C), and daily lows average 77°F (25°C). Daytime maximums rarely exceed 86°F (30°C) or drop below 81°F (27°C), while overnight minimums rarely fall below 75°F (24°C) or rise above 79°F (26°C).
Temperatures stay remarkably stable across the month, with a variation of less than 2°F between the first and last week. The slight upward trend begins around mid-September, when the southeast trade winds weaken, reducing their cooling effect on the islands.
Compared with April, the hottest period of the year, September is roughly 4°F cooler at peak hours. Compared with August, the coolest month, September is around 1–2°F warmer. The temperature range stays within the narrow tropical envelope typical of Seychelles, which experiences only minor seasonal swings due to its near-equatorial location.
Indoor comfort during September is generally good with natural ventilation. Air conditioning is needed at night only during the warmest weeks and rarely during the day.
Sea Temperature and Swimming Conditions
The Indian Ocean around Seychelles averages 81°F (27°C) in September, with a weekly variation of only 1–2°F. Water temperatures are comfortable for swimming throughout the month without thermal protection.
Sea temperature stays stable in September because the southeast trade wind, while still active, has lost most of its cooling power by this point in the season. The water is warmest in lagoons and protected bays, where readings can reach 83°F (28°C) during calm afternoons.
Underwater visibility ranges between 50 and 80 feet (15–25 meters) at the most popular snorkeling and dive sites. Visibility improves steadily through September as plankton levels drop and the surface is no longer churned by strong winds.
Seaweed is generally absent from inner-island beaches in September. The occasional drift of sargassum that affects other parts of the Indian Ocean rarely reaches the Seychelles archipelago at this time of year.
Rainfall and Rainy Days in September
September receives 90–110 mm of rain on average, distributed across 8–10 rainy days. This places the month among the drier periods of the Seychelles calendar, well below the December–February peak when monthly totals can exceed 300 mm.
Rain in September typically falls as short showers lasting 15–30 minutes rather than sustained tropical storms. Most showers occur in the late afternoon or early evening, leaving mornings reliably clear for outdoor activities and water sports.
The total monthly rainfall declines throughout the month. Early September records slightly higher totals than the final week, when the seasonal shift toward the drier inter-monsoon begins to take effect.
Heavy storms are uncommon. Thunder and lightning occur occasionally with afternoon convective clouds, but prolonged heavy rain events are rare in September compared with the northwest monsoon months.
Humidity Levels in September
Relative humidity averages 75–80% in September, placing the air in the "muggy" category on standard comfort scales. Morning readings can reach 85%, dropping to 65–70% during the warmer midday hours.
Humidity in September is lower than during the northwest monsoon months of December through March, when relative humidity can exceed 85% for extended stretches. The southeast trade wind helps reduce humidity by moving drier air across the islands.
The combined effect of 84°F air temperatures and 75–80% humidity produces a heat index of around 89–92°F (32–33°C) during the warmest part of the day. This level is well tolerated for most outdoor activities, especially in coastal areas where sea breezes provide additional cooling.
Sleep comfort during September is generally good. Nighttime humidity rises slightly, but lower air temperatures and active trade winds keep conditions tolerable without air conditioning in most accommodations.
Wind, Waves, and Sea State
Average wind speed in September is 11–13 mph (18–21 km/h), blowing predominantly from the southeast. The southeast trade winds weaken gradually throughout the month, with early September showing stronger and more consistent gusts than late September.
Wind speeds reach their highest values in the open channels between islands, where unobstructed exposure to the trade wind can produce sustained 15–18 mph (24–29 km/h) gusts. Sheltered bays and west-facing coastlines record much lower speeds, often below 8 mph (13 km/h).
Wave heights in September average 3–5 feet (1–1.5 meters) on east-facing coastlines and exposed channels. West-facing and leeward beaches stay calm, with typical wave heights below 1.5 feet (45 cm), making them better suited for swimming and water sports.
The asymmetric sea state has direct practical consequences. East-facing beaches such as Anse Source d'Argent on La Digue and parts of east Mahé experience moderate surf, while west-facing locations like Beau Vallon on Mahé and Anse Lazio on Praslin remain consistently calm.
Sunshine Hours, Daylight, and UV Index
September averages 6–7 hours of direct sunshine per day. Daylight runs approximately 12 hours, with sunrise near 6:10 AM and sunset around 6:15 PM throughout the month, reflecting the near-equatorial position of the Seychelles archipelago.
UV index values in September reach 11 or higher during midday hours, classified as extreme on the World Health Organization scale. UV exposure remains hazardous even under partial cloud cover, since solar radiation passes through thin tropical clouds with minimal attenuation.
Sun protection is essential for outdoor activity between 10 AM and 3 PM. Recommended measures include SPF 50+ broad-spectrum sunscreen, UV-rated sunglasses, a wide-brimmed hat, and reapplication every 90 minutes when in or near water.
Cloud Cover in September
Cloud cover in September decreases from approximately 57% of daylight hours at the start of the month to 52% by the end of the month. This reduction is part of the seasonal transition out of the southeast monsoon, when persistent trade-wind cumulus clouds gradually thin out.
Mornings in September are typically the clearest part of the day. Convective clouds build up after midday heating peaks, reaching their thickest stage between 2 PM and 5 PM before dissipating after sunset.
Cloud cover correlates directly with rainfall patterns and slight temperature dampening. Days with thicker afternoon cloud cover record cooler peak temperatures by 1–2°F and a higher probability of brief rain showers.
September Weather by Island — Mahé, Praslin, and La Digue
The climate across the three main inner islands of Seychelles is broadly similar in September, but microclimatic differences exist due to topography and exposure to the southeast trade wind. The mountainous interior of Mahé produces slightly more rainfall than the lower-lying islands of Praslin and La Digue.
Mahé records 100–120 mm of rainfall in September, with the highest totals on east-facing slopes and the central highlands around Morne Seychellois. West coast beaches such as Beau Vallon and Port Launay receive less rainfall due to the rain shadow effect of the central mountain range.
Praslin averages 80–95 mm of rainfall in September, with rainfall more evenly distributed across the island. Wind exposure is lower than on Mahé due to flatter terrain, and east-facing beaches such as Anse Volbert experience moderate surf while Anse Lazio on the north coast stays mostly calm.
La Digue receives 75–90 mm of rainfall in September, the lowest among the inner islands. The west coast beaches near La Passe and Anse Source d'Argent remain protected from the trade winds, while east-facing Grand Anse and Petite Anse experience the strongest swells.
Outer islands such as Alphonse, Desroches, and the Aldabra group lie further south and west, with slightly different patterns. These remote atolls typically record lower rainfall and lighter winds than the inner islands in September, with sea conditions improving earlier in the seasonal transition.
How September Compares to August and October
September sits between two distinct phases of the Seychelles climate cycle. August represents the peak of the cool, windy southeast monsoon, while October marks the transition into the warm, calm inter-monsoon period.
The differences across these three months can be summarized as follows.
|
Parameter |
August |
September |
October |
|
Avg high temperature |
82°F (28°C) |
84°F (29°C) |
86°F (30°C) |
|
Avg low temperature |
76°F (24°C) |
77°F (25°C) |
78°F (26°C) |
|
Sea temperature |
79°F (26°C) |
81°F (27°C) |
82°F (28°C) |
|
Monthly rainfall |
80–95 mm |
90–110 mm |
130–160 mm |
|
Rainy days |
7–9 |
8–10 |
11–13 |
|
Avg wind speed |
13–15 mph |
11–13 mph |
7–9 mph |
|
Cloud cover |
60% |
52–57% |
50–55% |
September offers a balanced combination of moderate winds, warm seas, and limited rainfall compared with August's stronger winds and October's higher rainfall. Travelers prioritizing dry weather find late September the most favorable window in this trio.
Is September a Good Time to Visit Seychelles
September is a strong month for visiting Seychelles. It combines warm air temperatures, manageable rainfall, comfortable sea conditions along leeward coasts, and lower tourist volumes than the December–February peak season.
The primary advantages of a September visit fall into four areas:
- Warm but not extreme heat, with daytime temperatures around 84°F
- Limited rainfall, averaging 8–10 rainy days of mostly short showers
- Quieter beaches and resorts due to off-peak demand
- Lower rates on accommodations and yacht charters compared with high season
The main limitations stem from the trailing southeast trade winds. East-facing beaches remain exposed to moderate surf; water sports on windward shores can be affected, and some snorkeling sites experience reduced visibility on stronger wind days.
September suits several traveler profiles well. Families benefit from quieter resorts and stable temperatures. Honeymooners find calm conditions on west-coast beaches without high-season crowds. Divers gain from improving underwater visibility. Anglers benefit from the seasonal presence of sailfish and tuna in offshore waters. Sailors and yacht-charter guests enjoy moderate wind that supports sailing without rough conditions.
Travelers who prefer completely flat seas, zero risk of rain, and peak underwater visibility may consider October or November instead, when the inter-monsoon period brings calmer conditions along all coastlines.
Best Activities for September Weather
September supports a wide range of water and land-based activities, with conditions improving steadily as the month progresses. Underwater visibility increases, the sea calms toward late September, and the wind weakens enough to make most outdoor pursuits comfortable.
Diving and snorkeling are well supported in September. Water temperatures of 81°F allow long sessions without thermal protection, and visibility of 50–80 feet permits clear sightings at popular sites such as Shark Bank, Brissare Rocks, and the Aldabra reef system. Late September delivers the best visibility of the month.
Beach activities depend heavily on coastal orientation. West-facing beaches stay calm and are well-suited for swimming, sunbathing, and shallow-water sports. East-facing beaches see moderate surf and stronger winds, making them better for kitesurfing and windsurfing than for swimming.
Fishing is productive in September. Offshore waters hold sailfish, yellowfin tuna, dogtooth tuna, and wahoo during this transitional period. Reef fishing also yields good catches of grouper, snapper, and emperor in waters around the inner islands.
Sailing and yacht charters operate effectively in September with route planning that accounts for the residual southeast wind. The protected channels between Mahé, Praslin, and La Digue offer calm conditions for short trips, while open passages to the outer islands require attention to weather windows.
Hiking and land excursions are comfortable in September. The Morne Seychellois National Park on Mahé and the Vallée de Mai on Praslin can be explored without the intense heat of April–May or the risk of rain in December–January. Early-morning starts offer the best conditions before midday, when humidity builds.
Sailing and Yacht Charters in Seychelles in September
September is suitable for yacht charters across the Seychelles archipelago, with itinerary planning adjusted to the prevailing southeast trade winds. East-facing coastlines retain moderate swells through most of the month, while west-facing and leeward shores stay calm and well-suited for anchoring and water-based activities.
Sea state directly shapes the comfort of onboard time. Average wind speeds of 11–13 mph and wave heights of 3–5 feet on exposed routes are within the comfort range of most charter vessels above 40 feet, with motion noticeably reduced on yachts of 55 feet and larger. Protected routes between the inner islands experience much smaller waves, typically under 2 feet.
Route selection depends on the passage's orientation. The recommended September routing follows the leeward sides of the islands: Mahé to Praslin via the inner channel, then onward to La Digue and the smaller satellite islands such as Curieuse and Cousin. This corridor offers protected anchorages and calm swimming stops at Anse Lazio, Anse Georgette, and Anse Source d'Argent.
Several types of charter trips work well in September. Half-day cruises around Mahé bays remain calm and well-suited for groups, including children. Full-day trips to Praslin and Curieuse offer enough time for snorkeling stops and beach landings. Multi-day liveaboard charters become more comfortable from mid-September onward as wind decreases, allowing relaxed island-hopping itineraries with overnight anchorages in sheltered bays.
The most reliable operating window during the day is in the morning. Wind speeds typically stay lower before midday, the sea is at its calmest, and the brief afternoon showers that occasionally develop are mostly avoided. Charters planned to depart between 8:00 AM and 9:00 AM and return by 4:00 PM, aligning well with September weather patterns.
CharterClick offers a fleet of yachts across multiple sizes and configurations available for September bookings throughout the Seychelles archipelago. The platform handles vessel selection, captain and crew arrangements, route-planning advice, and standard onboard services, including refreshments, snorkeling equipment, and water sports gear. Bookings can be arranged for hourly charters, full-day trips, or multi-day itineraries, depending on the type of experience.
What to Pack for September in Seychelles
Packing for September should match the warm temperatures, moderate trade winds, occasional afternoon showers, and extreme UV exposure that characterize the month. The combination calls for lightweight, breathable clothing supplemented by sun protection, rain accessories, and a light layer for evenings.
Clothing should be light and breathable. Linen and cotton shirts, breathable trousers, swimwear, and sandals cover most daily needs. A long-sleeved garment is useful for evenings on the water or in air-conditioned interiors.
Sun protection is non-negotiable. Recommended items include SPF 50+ reef-safe sunscreen, UV-rated sunglasses, a wide-brimmed hat, and lip balm with sun protection. Reapply sunscreen every 90 minutes during outdoor exposure and after every swim.
Activity-specific equipment depends on plans. Snorkel sets, water shoes, dry bags for beach excursions, and a reusable water bottle are practical for water-based days. Hiking shoes with grip are useful for trails in Morne Seychellois National Park and Fond Ferdinand on Praslin.
Rain accessories should be lightweight rather than heavy-duty. A compact rain jacket or travel umbrella handles the typical short afternoon showers without taking up significant space. Quick-drying fabrics reduce inconvenience after sudden rain.
A light windbreaker is useful for boat trips and evening dinners. Onboard wind speeds, combined with sea spray, can make it feel cool even at an air temperature of 80°F, especially after sunset.