Short answer
Krabi's rainy season runs from about May to October, when the province receives roughly 1,760 mm of its 2,220 mm yearly rain, according to the 1991 to 2020 normals. Island boat tours still run on many days, but the sea can be rough: Thailand's weather service expected waves of about 2 metres from Krabi southward in May 2026, and the national park has shut its beaches for days at a time. Our 4 Islands day is from $35 per person, and the operator moves or refunds any trip when the sea is unsafe.
The rainy season runs from May to October
The numbers draw a clear line. In the World Meteorological Organization's 1991 to 2020 normals for the Ko Lanta station, the Krabi-province station in the set, April brings 121.6 mm of rain. May jumps to 227.5 mm, and each month from June to October brings 285 mm or more. The six months from May to October bring about 1,760 mm of the station's 2,220 mm yearly total, roughly 79 per cent.
August is the wettest month at 342.0 mm, September follows with 319.4 mm, and October has the most rainy days, 17.9 of 31. In November the rain falls to 148.4 mm on 12.3 days, and in December to 64.6 mm. At the other end, February is driest with 24.1 mm on 1.8 days. The season is long, but it is not one block of weather every day.
What the sea does between May and October
The cause is the south-west monsoon. In an advisory dated 27 May 2026, the Thai Meteorological Department said the rather strong monsoon prevailed over the Andaman Sea, with waves of 2 to 3 metres from Phuket northward, and above 3 metres in thundershowers. For the lower Andaman Sea from Krabi downward it expected waves of about 2 metres, and more in thundershowers. It told small boats in the upper Andaman Sea to keep ashore.
So Krabi sits on the calmer side of that line, but it is not a flat sea, and thundershowers push the waves higher. Advisories like this one are issued repeatedly through the season, so the sea on your day may be better or worse. Our guide to seasickness on speedboat tours has practical advice.
When the park shuts the beaches
On the worst days the national park closes sites. The Thaiger reported on 20 September 2024 that the park temporarily closed its marine attractions for four days, from 19 to 22 September, after strong wind and waves of more than 4 metres. Red flags went up at Phi Phi Leh, Bamboo Island, Talay Waek and Poda Island, over 200 tour boats sheltered in Khlong Son Bay, and ferries between Krabi town and Phi Phi were suspended.
Poda is one of the stops on our 4 Islands day, so a closure like this affects the tour. We found no official rule that closes Poda or the Hong Islands for the whole rainy season. What the sources show is closures on rough days, decided by the park on the day. If your date falls in one, the operator moves the trip to another date or refunds it.
Which parks close for the season
Some Andaman parks do close for months. The Tourism Authority of Thailand explained in February 2018 that several national parks close every year between March and December, usually in the middle of the monsoon. It named Mu Ko Surin, Mu Ko Similan and, in Krabi's Mu Ko Lanta National Park, the Ko Ha and Ko Rok dive sites. The Department of National Parks confirmed then that Phi Phi would stay open.
On 15 October 2026 the Department said the Andaman marine-park season was officially open again, after the seasonal closure, naming the Similan and Surin parks, Hat Noppharat Thara–Mu Ko Phi Phi and Mu Ko Lanta among those ready for visitors. Maya Bay has its own closure: the Department's September 2026 report put it at 1 August to 30 September 2026. Read Maya Bay rules and closure for the details.
How our 4 Islands and Hong Islands days work in the rain
Both days run from Ao Nang by speedboat. The 4 Islands tour is from $35 per person, about 6 hours, back at about 2:00 pm; the Hong Islands tour is from $40 per person, about 7 to 8 hours, back at about 3:30 pm. A minibus collects you between about 7:30 and 8:40 am and the boat leaves the pier at about 9:00. Our 4 Islands or Hong Islands guide compares them.
The national park fee is paid in cash at check-in: 200 baht per adult and 100 per child on the 4 Islands tour, 300 and 150 on the Hong Islands tour. Jellyfish appear in some seasons, and the operator advises long swimwear and water shoes. Fins are not provided. If the sea is unsafe, the operator moves the trip to another date or refunds it.
Who should book in the rainy season, and who should not
A rainy-season boat day suits flexible travellers: you have several days in Krabi, you can move the date, and you accept a grey sky or a shower on the beach. It does not suit someone with one free day before a flight, or a person whose trip depends on a calm, clear sea. Our operator also does not recommend the tour for infants under 4, pregnant women or people with back or neck problems, which counts for more on a bumpy day.
The sandbar between Tup Island and Chicken Island is another reason to stay flexible: it appears at low tide, and at high tide you see it from the boat. That depends on the tide, not the season, but it is one more thing your day cannot promise. Ask us on WhatsApp for the best day in your week before you pay.
Planning a wet week in Krabi
Book your boat day early in the stay, not on the last day, and keep one spare day. Check the Thai Meteorological Department advisories the evening before. Add one or two land plans that do not depend on the sea; the Ao Nang things to do guide and Krabi with kids guide list some, and rain gear does most of the work.
If your dates are flexible, compare months before you commit. The same normals show Krabi at its driest from January to March, with 2 to 5 rainy days a month, and our best time to visit Krabi guide goes month by month. If you can only travel in the wet months, the Gulf coast is often drier from June to September, as the Andaman or Gulf coast guide explains.
Practical checklist
- Keep one spare day in your Krabi week for the boat trip, and book it early in your stay.
- Check the Thai Meteorological Department advisories the evening before the trip.
- Bring cash for the national park fee: 200 baht per adult on the 4 Islands tour, 300 on the Hong Islands tour.
- Pack quick-dry clothes, water shoes and a dry bag, because fins are not provided.
- Wear long swimwear if jellyfish are reported on your day.
- Avoid Maya Bay plans between 1 August and 30 September.
Questions and answers
Do island tours run in Krabi in the rainy season?
Yes, on days when the sea is safe. The national park can close beaches for days when waves are high, so trips are moved or refunded. Our 4 Islands day is from $35 per person.
When is the rainy season in Krabi?
About May to October. The 1991 to 2020 normals for the Ko Lanta station show 227.5 mm in May and a peak of 342.0 mm in August, with 14 to 18 rainy days a month.
How rough is the sea in Krabi in the rainy season?
On 27 May 2026 the Thai Meteorological Department expected waves of about 2 metres from Krabi downward, and 2 to 3 metres from Phuket northward. They are higher in thundershowers.
Is Poda Island closed in the rainy season?
We found no official full-season closure. In September 2024 the park raised red flags at Poda for four days because of rough seas, so it can close at short notice.
What happens if my Krabi boat trip is cancelled?
If the sea is unsafe, our operator moves the trip to another date or refunds it. Tell us your dates and hotel, and we confirm the plan on WhatsApp before you pay.
Is it worth going to Krabi in October?
October has the most rainy days of the year, 17.9, and 297.5 mm of rain. The Andaman park season opened officially on 15 October 2026, but expect a wet week.