⛱️ Weather in Thailand in May: rain, sea temperature and resort choice

In May, the weather in Thailand changes almost exactly on schedule. The first half of the month is still dry, and in mid-May the meteorological service officially announces the start of the rainy season. It names the exact date anew each year (as of 05/2026, announcement by the Thai meteorological service).

Rainfall is uneven across the country: in May, Bangkok receives about 201 mm (as of 09/2026, Bangkok climate tables), Phuket about 263 mm, and Pattaya about 143 mm. Below we break down four resort areas: how many rainy days to expect, air and water temperatures, sea risks, and one practical takeaway for each location.

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May in Thailand: how the rainy season begins

The southwest monsoon reaches the Andaman Sea and the Gulf of Thailand in mid-May, and the rains last almost until the end of October (as of 05/2026, meteorological service report on the season start). They do not fall evenly: the north of the country gets short drizzle, while the south and the coast get real downpours with thunderstorms that start suddenly and end just as quickly.

💡 In short:

Until mid-May, rains are still rare, so the beginning of the month works well for a beach vacation.
In the second half of May, rain becomes a daily backdrop, and you should plan your day with room for a wet hour.

In practice, a May day looks like this. The morning stays clear and hot, by noon the sky clouds over, and after four o'clock a wall of water hits the city for about forty minutes. An hour later the streets are dry, the humidity remains high, and by evening it is warm again.

May is harder with children than the winter months: high humidity and heat create favorable conditions for infections, and the sudden weather changes wear out little ones. If you cannot postpone a trip with children, book a hotel with air conditioning and a pool, and schedule long walks for the morning.

Sea, jellyfish, and surf waves

Water temperature in May barely changes and stays comfortable for swimming, so the issue here is not cold but waves and murkiness. After every downpour, the water near open shores turns murky, and a current runs along the bottom that you cannot see from the beach.

One May-specific feature worth planning for in advance is jellyfish. Near the coast they gather in colonies, and after a storm there are more of them. Check the flag at the lifeguard tower: red means you should not enter the water, even if the sea looks calm.

Surfers, on the other hand, get their conditions on the Andaman coast in May. The waves hold steady there, and it is the only beach sport that rain does not disrupt. Everyone else should remember a simple rule: swim between the flags and do not go far from the shore.

Phuket: 263 mm of rain and strong currents

Phuket receives about 263 mm of rainfall in May over roughly 22 rainy days (as of 09/2026, Phuket climate tables). Daytime air stays around 30 °C, nighttime around 27 °C, so you will not get any cool relief even after sunset.

The main caution in Phuket has to do with water, not rain. Prolonged downpours create strong underwater currents near the western shores that can pull you out to open sea, so choose beaches with a lifeguard on duty and do not leave children unattended near the water.

With accommodation, the logic is simple: if you are going on a short trip, stay near the beach you want, because crossing the island takes time, and in the rain it takes even longer. See Phuket hotels on Trip.com.

Pattaya: short downpours in the afternoon

Pattaya in May is noticeably drier than Phuket: about 143 mm of precipitation over 13 rainy days (as of 09/2026, Pattaya rainfall tables). Downpours here are short and mostly come in the second half of the day, so the first half of the day is free for the beach.

Pattaya Bay with boats under a cloudy sky

The heat does not let up, though: around 33 °C during the day and around 28 °C at night (as of 09/2026, Pattaya climate data). It is better to sunbathe before eleven in the morning, and after lunch plan shopping malls, a massage, or a trip to temples where you can wait out the rain under a roof.

Hotels in Pattaya line the entire seafront, and the price depends on the distance to the sea. Find Pattaya hotels on Trip.com.

Koh Samui: steady heat and short rains

Koh Samui gets about 126 mm of precipitation over 17 rainy days in May (as of 09/2026, Koh Samui climate tables). Around 31 °C during the day and around 28 °C at night, and this steady heat lasts for weeks: the dry season here is short, roughly from February to April.

Panoramic view of Samui beach with sea and palm trees

Rain on Koh Samui does not cancel swimming, because the downpours here are short and barely cool the air. You should choose a hotel with working air conditioning and a pool: after a stuffy night, that is not a luxury but a necessity.

Compare Koh Samui hotels on Trip.com.

Bangkok: humid heat with no nighttime cool-down

Bangkok gets about 201 mm of precipitation over 14 rainy days in May (as of 09/2026, Bangkok rainfall norms). Around 36 °C during the day and around 28 °C at night, and because of the city's low elevation, the hot air stagnates and does not have time to cool off overnight.

It is best to schedule Bangkok tours for the morning, when you can reach the temples before the first wave of rain. In the afternoon, choose indoor places: shopping malls, museums, and markets where the rain cannot reach you.

See Bangkok hotels on Trip.com.

⁉️🤔 Frequently asked questions

Is it worth going to Thailand in May?

Yes, if you are ready for daily downpours in the second half of the month. The first half of May is almost rain-free, the sea stays warm, and hotel prices are lower than in high season. Choose Pattaya or Samui if you want more sunny hours and fewer wet walks.

Where does it rain the least in May?

Samui gets the least rainfall, about 126 mm per month. Pattaya gets about 143 mm, but it has fewer rainy days (as of 09/2026, Pattaya rainfall statistics). Phuket and Bangkok get noticeably more rain. The difference becomes clear within the first days of your trip, so you will quickly figure out which resort suits you.

Can you swim in Phuket in May?

You can swim, but with some caveats. The sea is warm all year round, but after prolonged downpours, underwater currents strengthen along the western shores and the water becomes murky. Swim between the flags, choose beaches with a lifeguard on duty, and do not enter the water when a red flag is up.

How long do downpours last in Thailand in May?

A downpour usually lasts from half an hour to two hours and ends just as suddenly as it began. Between waves of rain you have time to walk around, because the air stays warm and the streets dry quickly. Multi-day steady rains also happen, but less often.

What is the weather like in Samui and Bangkok in May?

Samui holds steady heat: about 31 °C during the day and about 28 °C at night (as of 09/2026, Samui climate data). Bangkok is hotter and more humid: about 36 °C during the day, and the air barely cools down at night. Rain in both cities comes in short waves, more often in the afternoon.

In short: what to book

If you are traveling in the first days of May: choose Phuket or Samui while rain is still rare. If your vacation falls at the end of the month: choose Pattaya or Samui. Pattaya has fewer rainy days, and Samui gets the least rainfall. If you are traveling with children: a hotel with a pool and air conditioning matters more than being close to the beach. If rain disrupts your plans: GetYourGuide tours will help fill the wet days, and you will find hotels for each resort through the links above.

Thailand in May: 263 mm of rain in Phuket and where rains are shorter