Mirissa weather in August

August in Mirissa: hot, soaked, with clean air — fine if you can take 25 rainy days.

Updated September 2026 · climate normals from ERA5 reanalysis

Mirissa🇱🇰 Sri Lanka · Sri Lanka & the Maldives · Beach80
  1. 83Jan
  2. 89Feb
  3. 85Mar
  4. 79Apr
  5. 66May
  6. 77Jun
  7. 81Jul
  8. 80Aug
  9. 76Sep
  10. 70Oct
  11. 64Nov
  12. 78Dec

#5 of 12 months in Mirissa · #687 of 1413 destinations to visit in August · comfort 80/100 (tier A)

Days
29°C
Nights
25°C
Wet days
25
Sun
10.4 h
Humidity
86%
Daylight
12 h
Mirissa, Sri Lanka
Photo: Mohamed Shafraz · Pexels

Traveller notes on Mirissa in August

Forum posters describe August as generally sunny with around 5-6 hours of good sunshine after breakfast, and typically just an odd late-afternoon or evening shower rather than sustained rain - genuinely pleasant weather on land. Posters are consistent, though, that the sea itself runs too rough for safe swimming along most of this stretch of coast in August, with only reef-protected beaches like Hikkaduwa and Unawatuna, or the small reef-sheltered patch just west of Mirissa, offering calmer water. Posters generally describe August-into-September as a genuinely good time to be in Mirissa overall, provided visitors accept the rough sea and skip ocean swimming in favor of beach time and reef-protected spots elsewhere along the coast.
Tripadvisor community · August · 1 month ago · Read more on Tripadvisor ↗

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.
WeligamaBayAprilRegular · April · 1 month ago · Read more on Tripadvisor ↗
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.
WeligamaBaySecondMonsoon · November · 1 month ago · Read more on tripadvisor.co.nz ↗
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.
ReefProtectedMirissaJuly · July · 1 month ago · Read more on Tripadvisor ↗
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.
MorningsAreTheGoodHalf · January · 1 month ago · Read more on Tripadvisor ↗

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Mirissa climate normals — August

Daytime high29°C / 84°F🥵 hot
Nighttime low25°C / 78°F
Feels like (high)33°C / 91°F
Sea temperature28°C / 83°F♨️ bath-warm
Rainfall155 mm / 6.1 in⛈ soaked
Rainy days25 days
Humidity86%💦 very humid
Dew point25°C / 76°F
Sunshine10.4 h/day
Daylight12.3 h
Wind24 km/h / 15 mph
Air quality (US AQI)46🍃 good

Monthly averages from ERA5 reanalysis. AQI is the mean US Air Quality Index for the month.

Crowds in Mirissa in August

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 4 of the markets that fill it(estimated)

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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.

JFMAMJJASOND

Best weatherFair weatherToughest weather

What's on in Mirissa in August

Recurring seasonal events, natural spectacles, closures and holidays — curated and sourced.

  • Season

    Southwest (Yala) monsoon

    15 May – 15 Sep · usuallyRisk

    The 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.

What's on around the world in August →

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?

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Mirissa in August — FAQ

Is August a good time to visit Mirissa?
August in Mirissa: hot, soaked, with clean air — fine if you can take 25 rainy days. It ranks #5 of 12 months for Mirissa on SeasonMap's comfort score (80/100).
What is the weather like in Mirissa in August?
In August, Mirissa averages a daily high of 29°C and a low of 25.4°C, with about 155 mm of rain over roughly 25.2 rainy days.
What is the air quality in Mirissa in August?
Mirissa has a mean US Air Quality Index of about 46 in August.

Within 300 km: Colombo's Esala Perahera on 18–28 Aug, and Sigiriya's The Gathering at Minneriya around 15 Jul – 30 Sep.