May · Thailand weather
Thailand in May: Weather, What to Expect & Where to Go
Updated
May is the official start of the rainy season. Storms are heavy but usually short and predictable — an afternoon downpour, then sunshine. The Andaman coast gets the worst of it; the Gulf side stays mostly dry. Prices drop sharply.
Best region
Gulf
Samui and Phangan are still mostly dry, and noticeably less crowded than the winter peak.
Avoid
Andaman
The southwest monsoon hits the Andaman coast first — rough seas, heavy rain, dive boats stop running.
Good for
Gulf islands, fewer crowds, lower prices
May weather, region by region
Average temperatures and rainfall across Thailand's five climate regions in May. Tap the climate map on the homepage for an interactive month-by-month view.
| Region | Avg temp | Rainfall | Visit rating |
|---|---|---|---|
North Chiang Mai | 29°C | 170mm | Great |
Northeast Nakhon Ratchasima (Korat) | 30°C | 180mm | Good |
Central Bangkok | 30°C | 220mm | Good |
Andaman Phuket | 29°C | 280mm | Good |
Gulf Koh Samui | 30°C | 160mm | Great |
City spotlights
One city per region — what May actually feels like on the ground, and what to do or skip.
North
Chiang Mai
By the numbers
Chiang Mai averages 29°C — highs around 33°C, nights around 23°C. Around 170mm of rain across 14–15 days. The first storms finally wash the haze away.
The mountains turn green again. Late-afternoon light after the rain is some of the best photography light in Thailand.
The first storms wash the haze away — the mountains are green again. Cheaper rates, fewer tourists, and beautiful late-afternoon light after the rain.
Year-round climate
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Northeast
Nakhon Ratchasima (Korat)
By the numbers
Korat averages 30°C with afternoon highs of 34°C. Around 180mm of rain across 14–16 days. Khao Yai's waterfalls begin to swell.
First storms break the heat and green up the plateau. Khao Yai is at its most photogenic since the previous October.
First storms break the heat and green up the Korat plateau. Khao Yai's waterfalls start to swell — Haew Narok is impressive after a week of rain.
Year-round climate
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Central
Bangkok
By the numbers
Bangkok averages 30°C — highs around 34°C, nights 26°C. Around 220mm of rain across 17–18 days, mostly heavy late-afternoon storms. Humidity climbs to 80%.
Hot, sticky, and prone to dramatic storms. Flash flooding in low-lying neighbourhoods is common.
Hot, sticky, and prone to dramatic afternoon storms. Mornings are workable; evenings can flood with little warning.
Year-round climate
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Andaman
Phuket
By the numbers
Phuket averages 29°C with around 280mm of rain across 18–19 days. Sea visibility drops to 5–15m. Sea temperature stays at 29°C.
Monsoon arrives in earnest. Hotels are cheap, mornings can still be glorious, but you'll lose dive days.
Monsoon arrives in earnest. Hotels are cheap, mornings can still be glorious, but you'll lose dive days and risk a washout.
Year-round climate
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Gulf
Koh Samui
By the numbers
Koh Samui averages 30°C with around 160mm of rain across 11 days, mostly brief bursts. Sea temperature 30°C with calm conditions.
Hands-down the best beach option this month. Reliable sun on the dry side of the country.
Hands-down the best beach option this month. Dry side of the country, reliable sun, and shoulder-season pricing.
Year-round climate
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Events & festivals in May
Royal Ploughing Ceremony
An ancient ceremony at Sanam Luang in Bangkok marking the start of the rice-planting season. A national holiday with a public day off.
Where to actually go
Ten days in May
- 2days
Bangkok
Storms are predictable. Mornings are workable; afternoons need a contingency plan.
Train · 13h overnight sleeperBook on 12Go - 3days
Chiang Mai
The mountains are green and the haze is gone. Cheap and uncrowded.
Flight · ~3h with layoverBook on 12Go - 5days
Koh Samui
Peak Gulf beach weather. The country's most reliable May sunshine.
Skip a diving-focused Andaman trip this month. Save Phuket and Krabi for November–March.
Sea conditions in May
Thailand has two coastlines on opposite monsoon calendars. Here's what each looks like this month for swimming, diving, and boat trips.
Andaman coast — Phuket, Krabi, Phi Phi
Monsoon is here. Visibility drops to 5–15m, dive operators wind down, long-tail trips become weather-dependent. Hotel rates collapse.
Gulf coast — Samui, Phangan, Tao
Still excellent. Sea temperature 30°C, calm mornings, diving on Koh Tao at peak with 20–25m visibility.
How crowded is Thailand in May?
Big shift to shoulder-season pricing. Phuket and Krabi hotel rates drop 30–50% from peak; Chiang Mai and Bangkok are quietly comfortable. Koh Samui stays busier as the rest of the country shifts.
What to pack for Thailand in May
- A compact rain jacket — afternoon storms are routine almost everywhere
- Quick-dry travel clothes (cotton stays wet for days)
- Water-resistant shoes or sandals
- Modest temple-visit outfit
- Insect repellent — mosquitoes become noticeably more active
May is the start of the rainy season but storms are typically heavy and short — an afternoon downpour followed by sunshine, not all-day grey. Plan outdoor activities for mornings and you'll rarely lose a full day.
Thailand in May — common questions
Is May a good time to visit Thailand?
Yes, if you're flexible on weather. May is the start of the southwest monsoon — heavy afternoon storms are routine on the Andaman coast and in Bangkok, but the Gulf islands stay dry. Prices drop sharply from April's peak, crowds thin out, and the country looks alive after the dry season. A budget-friendly shoulder month for travellers who don't need guaranteed sunshine.
Is May rainy season in Thailand?
Yes — May is the official start of the southwest monsoon. The Andaman coast (Phuket, Krabi) gets the heaviest rain, Bangkok sees daily afternoon storms, and the north turns green. The Gulf coast (Koh Samui, Phangan) is on a flipped calendar and stays dry through May.
Can you still go to Phuket in May?
Yes, but with caveats. Hotel prices are at their lowest of the year and mornings are often still bright, but dive operators wind down, sea visibility drops to 5–15m, and rough surf makes some beaches unsafe. If diving is the priority, choose Koh Tao or Koh Samui instead this month.
How hot is Bangkok in May?
Bangkok averages 30°C with afternoon highs of 34°C and overnight lows of 26°C. The heat eases slightly from April's peak as afternoon storms cool the city, but humidity climbs to 80% — it feels muggier than April even though the absolute temperature is lower.
Is the Gulf coast a good idea in May?
Yes — May is one of the best months for Koh Samui, Phangan, and Tao. The Gulf islands run on a flipped weather calendar from the Andaman coast: dry from January through August, wet from October through December. May falls in the peak of the Gulf's dry season.
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