Koh Samui in July: Weather, Sea and What's On

Koh Samui in July is a good bet: it's warm, the sea sits close to 30°C, and prices are noticeably lower than in high season. The trade-off is a few more clouds and short, sometimes heavy afternoon showers – not day-long rain. Boat tours, snorkelling and Ang Thong Marine Park all run as normal, though the island gets a touch busier around the late-July public holidays.

At a glance

Weather in July

July isn't yet part of Koh Samui's real rainy season – on the Gulf side that runs from October to December. In July, showers tend to arrive as short but heavy afternoon or evening downpours, while mornings are usually sunny. The east coast (Chaweng, Lamai, Choeng Mon) sits sheltered and generally stays calm; the west coast (Nathon, Taling Ngam) can pick up more wind and swell from the south-west monsoon, which at this time of year is hitting the Andaman coast around Phuket and Krabi. For Koh Samui itself, that means good swimming and boating conditions with the usual dose of tropical unpredictability.

What you can do in July — and what you can't

Ang Thong Marine Park is open as normal in July (its only 2026 closure runs from 1 November to 15 December), and the sea on the Gulf side is usually calm enough for day trips. Snorkelling tours to the southern islands or to Koh Tao/Koh Nang Yuan also run without restriction. What doesn't always go to plan: a sunset boat tour fixed to one exact date when a thick cloud bank rolls in – it pays to stay flexible on timing.

One of the most popular full-day tours heads to Ang Thong Marine Park: hotel pick-up between 07:00 and 08:00, the speedboat departs from Bangrak around 09:00, and after around 60 minutes you're snorkelling at Koh Wua Talap, followed by the viewpoint and Emerald Lagoon at Koh Mae Koh. Breakfast, lunch, soft drinks, snorkelling gear and kayaking are included; the park entrance fee (300 THB adults, 150 THB children) is paid locally:

from 1,850 THBAngthong Marine Park Full-Day Speed Boat VIP Tour★★★★★4.72 from 389 reviews

For something shorter, the Pig Island Economy Tour works well: pick-up around 08:30 or 13:00 depending on the programme, departing from Bang Khao in the south, with snorkelling on Koh Tan's coral reef and a visit to the swimming woolly pigs on Koh Madsum, including lunch or dinner and kayaking. The 50 THB island entrance fee is not included:

from 1,450 THBPig Island Snorkeling Koh Madsum & Koh Tan Speed Boat Economy Tour★★★★★4.79 from 283 reviews

For the full day out, the trip to Koh Nang Yuan and Koh Tao is hard to beat: pick-up between 07:20 and 08:20 in Bophut, around 90 minutes by boat, the famous postcard viewpoint on Koh Nang Yuan, lunch, and two snorkelling stops off Koh Tao. The Koh Nang Yuan entrance fee (250 THB adults, 100 THB children) is added locally:

from 1,850 THBDay trip snorkeling Koh Tao & Koh Nang Yuan★★★★★4.78 from 169 reviews

Festivals and events in July

July 2026 ends with a dense run of public holidays. 28 July is King Vajiralongkorn's Birthday, a national public holiday. Right after that come two Buddhist holy days with a nationwide 24-hour alcohol sales ban at shops and supermarkets: Asalha Bucha Day on 29 July marks the Buddha's first sermon, and 30 July is Khao Phansa, the start of the three-month Buddhist Rains Retreat that runs until 26 October 2026. Hotel bars, airport outlets and licensed venues in designated tourist zones can still serve alcohol on these days, but shops and supermarkets cannot sell it. The public holiday also brings more domestic visitors to the island that weekend, so expect slightly bigger crowds than the rest of the month.

Fruit in season

July markets and street stalls carry several fruits at their best: durian (main season runs to August/September) is still widely available, as are mangosteen and rambutan, both mid-season. Longan is just starting its main season in July, which continues through September. Papaya, jackfruit, dragon fruit, guava and coconut are available year-round. For more detail, including the rules on durian in hotels and what you can bring home, see our Top 10 fruits in Thailand.

Frequently asked questions

Does it rain a lot on Koh Samui in July?

With around 120 mm over about 11 days, July is well below what counts as the island's real rainy season (October to December). Most of it falls as short, heavy showers in the afternoon or evening rather than continuous rain.

Is July a good time to visit Koh Samui?

Yes. You get warm weather, sea temperatures close to 30°C, and lower prices than the December-to-April high season – just build in some flexibility around occasional showers.

Is Ang Thong Marine Park open in July?

Yes, it operates as normal. The only scheduled 2026 closure is from 1 November to 15 December, when the sea on the Gulf side is roughest.

What's happening on Koh Samui from 28 to 30 July?

A run of public holidays: the King's Birthday on the 28th, Asalha Bucha Day on the 29th, and the start of the Buddhist Rains Retreat (Khao Phansa) on the 30th. The last two carry a nationwide alcohol sales ban in shops, though hotel bars keep serving.

For the months either side, see Koh Samui in June and Koh Samui in August. The full climate table and an explanation of the Gulf-side rainy season are in Koh Samui weather and the truth about the rainy season, and an overview of every month is in The best time to visit Koh Samui.