Mirissa weather in September
September in Mirissa: hot, soaked, with clean air — fine if you can take 27 rainy days.
Updated September 2026 · climate normals from ERA5 reanalysis
#9 of 12 months in Mirissa · #826 of 1413 destinations to visit in September · comfort 76/100 (tier B)
- Days
- 29°C
- Nights
- 25°C
- Wet days
- 27
- Sun
- 10 h
- Humidity
- 86%
- Daylight
- 12 h

Traveller notes on Mirissa in September
Notes from nearby Nuwara Eliya (119 km away)
Mirissa doesn't have its own notes for September yet — these are about Nuwara Eliya, close enough to share the season.
Nuwara Eliya-forum threads on September weather describe this hill town as genuinely cool given its elevation, a real contrast to the lowland heat elsewhere, and posters are consistent this stretch of the year runs wetter, drizzly stints entirely possible across a multi-day stay. One visitor touring in the late-August-into-September window reported a couple of hours of light drizzle rather than a full washout, suggesting shorter showers rather than sustained downpours. Regulars call mid-September a reasonable sweet spot within the broader wet season, conditions gradually starting to balance out compared to the peak of the pattern. A proper jacket is standing advice regardless of forecast, evenings running genuinely chilly year round given the elevation. Posters call the tea country scenery and cooler climate worth the rain risk. The record: 19.5C days feeling like 19C, 13.4C nights, an extraordinarily high 166mm across 26 days and 84 percent humidity.
Other months in Mirissa
Mirissa-forum threads on April weather call it the last reliably good month on the south coast before the monsoon takes over - calm seas still holding for swimming and beginner surfing, though posters describe it as a genuine shoulder season where conditions can start slipping outside the reef-protected stretches of beach. Showers become more likely after the middle of the month, roughly a month ahead of when the real southwest monsoon breaks, typically arriving as a short afternoon or evening burst rather than an all-day soak. Regulars still rate plenty of sunshine across most days, humidity climbing but not yet unbearable. The standing advice is to front-load a south-coast beach stay for the first half of April if a trip's dates are flexible, since the back half carries noticeably higher odds of a wet afternoon. The record: 31.2C days feeling like a punishing 38C, 25.6C nights, a notably high 169mm across 25.6 days, 85 percent humidity, a 30.3C sea and 10.5 hours of sun.
Mirissa-forum threads on November weather place it inside the second inter-monsoon season - genuinely the wettest stretch of the year by rainfall total, and posters call conditions unsettled rather than predictable week to week. The one consistent pattern regulars point to: rain tends to arrive later in the day, leaving mornings sunny more often than the wet-season reputation implies, and the island still logs real total sunshine across the month. Sea conditions are the bigger practical concern - not calm enough most days for swimming on the open coast, though a few sheltered stretches of beach stay swimmable. Regulars steer visitors wanting reliable beach weather toward January through mid-March instead. The record: 29.6C days feeling like a sticky 35C, 24.4C nights, a notably high 306mm across 25.1 days, 87 percent humidity, an 8.8-hour sun day and a 29.3C sea - the wettest entry on Mirissa's whole calendar.
Hikkaduwa-and-Mirissa forum threads on July weather describe the south coast as manageable through the off-season rather than ideal: decent conditions most days, but evening showers are common and the sea runs genuinely rough, making swimming and snorkeling harder than in the calmer months. Mirissa gets called out specifically for having reef-protected sections of beach that stay swimmable even when the open coast doesn't, a real edge over neighboring beaches this time of year. Posters describe a reliable pattern - good weather most mornings, showers arriving later in the day in short bursts rather than settling in for hours. The record: 29.2C days feeling like a sticky 33C, 25.6C nights, 140mm across a notably high 25.4 days, an 85 percent humidity, a 26.5C sea and 10.5 hours of sun - the wettest, roughest entry on this destination's whole calendar, exactly matching the off-season framing.
January is the start of the good half of Mirissa's whale season: the south coast runs November to May, and regulars say sightings improve into January and February, which is the window they name for blue whales. Two practical points come with it. The boats leave early - reporting around half past six for a seven o'clock start, three and a half to four hours out - which is the reason to stay in Mirissa rather than Galle or Colombo. And the weather is not settled at the turn of the year: rain can hang on into mid-January, with the first half of the day the reliable part on this coast. Our row's 133.8mm across 16.3 days is that. The record: 30C days that feel like 36C, 23.8C nights, humidity 82 percent and a 27.6C sea.
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Mirissa climate normals — September
Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.
Crowds in Mirissa in September
How busy the place itself is — school and mass holidays, the months an editor tagged, and how sought-after the weather makes them. Never part of the comfort score.
BusyAugust break in Sri Lanka, school holidays in 3 of the markets that fill it(estimated)
Peak crowdsBusyShoulder seasonQuiet
Best months for Mirissa's weather
Ranked by this destination's own climate comfort score across the year — a different thing from how busy it gets (see Crowds above).
Fair weatherMirissa's weather peaks January–March, best around February.
Best weatherFair weatherToughest weather
What's on in Mirissa in September
Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.
- Season
Southwest (Yala) monsoon
15 May – 15 Sep · usuallyRiskThe whale boats stop, the bay picks up a heavy shore break and the sand narrows to a strip. Half the beach places board up; the ones that stay open charge a third of the winter rate.
Nearby, and something's on
Within 300 km of Mirissa — a day trip or a short hop — with something on this month. Never part of the comfort score.
Where is Mirissa?
Mirissa in September — FAQ
- Is September a good time to visit Mirissa?
- September in Mirissa: hot, soaked, with clean air — fine if you can take 27 rainy days. It ranks #9 of 12 months for Mirissa on SeasonMap's comfort score (76/100).
- What is the weather like in Mirissa in September?
- In September, Mirissa averages a daily high of 29.1°C and a low of 25°C, with about 191.4 mm of rain over roughly 26.5 rainy days.
- What is the air quality in Mirissa in September?
- Mirissa has a mean US Air Quality Index of about 40 in September.
Within 300 km: Sigiriya's The Gathering at Minneriya around 15 Jul – 30 Sep, and Colombo's East coast season around 1 May – 30 Sep.