Eleven years of monthly weather and wave data for Phuket, reduced to one table: how much it rains, how many days, whether the west-coast sea is swimmable, how hot, how sunny. No adjectives without a number.
Data: Open-Meteo (ERA5), 2015–2026, medians per calendar month over 2015–2025; file refreshed 2026-10-08. Waves from 2022-01.
Nov–Mar
North-east monsoon. Median rain per month 103 mm, daily highs around 29–31 °C, the Andaman flat: a median month has no rough-sea days at all. This is what the brochures mean by 'Phuket weather', and it is also when hotel rates and crowds peak.
Apr, Oct
April is the hottest, stickiest month (183 mm, sea still calm); October is the wettest-but-calming month (340 mm, the swell already dropping). Both are transition months rather than a season of their own, which is why we label them separately instead of pretending they belong to either side.
May–Sep
South-west monsoon. Median rain per month 288 mm, 25 rain days out of 30, and a swell on the west coast that makes some beaches unsafe for swimming on a third of the days. Rain usually comes in bursts of an hour or two, not all day — but 'it never rains all day' is a pattern, not a promise.
These are climate seasons. The index price seasons follow hotel rate calendars instead (high: November–April, low: May–October), so April counts as 'high' in the price tables and 'shoulder' here.
Events calendar → One page per month: what is on, the weather and sea normals, how busy it gets and what that does to prices.
Every cell is the median of 11 monthly values (one per year); sea columns use 4 years because wave data starts in 2022-01. Rain days count any day with measurable rain, so they run higher than 'rainy days' as a visitor would count them.
| Month | Season | Rain, mm | Rain days | Heavy-rain days | Sea | High, °C | Low, °C | Sun, h | Humidity, % |
|---|---|---|---|---|---|---|---|---|---|
| January | High season | 37 | 10 | 0 | calm · 0 days | 29.5 | 24.4 | 329 | 79 |
| February | High season | 21 | 7 | 0 | calm · 0 days | 30.7 | 24.7 | 312 | 74 |
| March | High season | 73 | 14 | 0 | calm · 0 days | 31.7 | 25.4 | 343 | 76 |
| April | Shoulder | 183 | 25 | 2 | calm · 0 days | 30.7 | 25.7 | 311 | 82 |
| May | Green season | 343 | 28 | 4 | some swell · 4 days | 29.8 | 25.6 | 298 | 86 |
| June | Green season | 275 | 22 | 4 | some swell · 8 days | 29.3 | 25.9 | 284 | 84 |
| July | Green season | 241 | 24 | 3 | rough · 13 days | 29.2 | 25.8 | 279 | 84 |
| August | Green season | 270 | 25 | 3 | rough · 9 days | 28.9 | 25.3 | 277 | 84 |
| September | Green season | 309 | 25 | 6 | rough · 12 days | 28.7 | 24.8 | 248 | 86 |
| October | Shoulder | 340 | 28 | 4 | calm · 2 days | 29.0 | 24.4 | 286 | 86 |
| November | High season | 270 | 27 | 3 | calm · 0 days | 28.7 | 24.5 | 260 | 87 |
| December | High season | 113 | 16 | 1 | calm · 0 days | 29.2 | 24.1 | 298 | 83 |
Weather: Open-Meteo (ERA5), 2015–2026, licensed CC BY 4.0, grid point 7.89°N 98.30°E. Waves: Open-Meteo marine model, from 2022-01. Normals are medians of the monthly values for 2015–2025; the 'last twelve months' table uses the raw monthly values. Rough-sea days are days whose modelled maximum wave height exceeds the pipeline's swimming-safety threshold. Nothing is interpolated: an empty cell means no observation.
daily highdaily low
| Month | Mean, °C | Lowest day | Warmest day | n years |
|---|---|---|---|---|
| January | 28.8 | 28.2 | 29.5 | 3 |
| February | 29.1 | 28.5 | 30.1 | 3 |
| March | 29.8 | 28.6 | 31.1 | 4 |
| April | 30.7 | 28.6 | 32.2 | 4 |
| May | 31.0 | 29.6 | 32.3 | 4 |
| June | 30.1 | 29.3 | 31.8 | 4 |
| July | 29.9 | 29.2 | 31.0 | 4 |
| August | 29.9 | 29.1 | 31.2 | 4 |
| September | 29.4 | 28.4 | 30.3 | 4 |
| October | 29.5 | 28.7 | 30.6 | 3 |
| November | 29.8 | 28.5 | 30.8 | 3 |
| December | 29.0 | 28.2 | 30.0 | 4 |
Warmest sea May (31.0 °C), coolest January (28.8 °C); median of the monthly means over the years on file, n per row. Sea, air and dengue →
| Month | Monthly mean | Worst day | Days > 37.5 | Days > 15 |
|---|---|---|---|---|
| August 2026 | 11.3 | 26.8 | 0 | 6 |
| July 2026 | 8.7 | 16.2 | 0 | 1 |
µg/m³ · Air4Thai, Pollution Control Department, Municipal Health Center, Talat Yai, Mueang Phuket; 0 of 62 measured days above Thailand's 24-hour standard (37.5 µg/m³). The history accrues one month per refresh from 2026-07. Sea, air and dengue →
October 2025 to September 2026: what actually happened, next to the eleven-year median for the same month. A single year is weather; the median is climate.
| Month | Rain, mm | Normal, mm | vs normal | Rough-sea days | Normal |
|---|---|---|---|---|---|
| October 2025 | 361 | 340 | +6% | 3 | 2 |
| November 2025 | 271 | 270 | 0% | 1 | 0 |
| December 2025 | 76 | 113 | -33% | 0 | 0 |
| January 2026 | 10 | 37 | -73% | 0 | 0 |
| February 2026 | 74 | 21 | +252% | 0 | 0 |
| March 2026 | 26 | 73 | -64% | 0 | 0 |
| April 2026 | 57 | 183 | -69% | 0 | 0 |
| May 2026 | 314 | 343 | -8% | 9 | 4 |
| June 2026 | 320 | 275 | +16% | 4 | 8 |
| July 2026 | 153 | 241 | -37% | 8 | 13 |
| August 2026 | 108 | 270 | -60% | 18 | 9 |
| September 2026 | 230 | 309 | -26% | 4 | 12 |
Most 'best time to visit Phuket' pages repeat a chart copied from a chart copied from a tourist-board leaflet. The numbers on this page are computed from a reanalysis dataset — a weather model constrained by satellite and station observations — for one grid point on Phuket's west coast, month by month, from January 2015 to the latest complete month. For each calendar month we take the median of the yearly values: the middle value, not the mean, so one freak month (a tropical storm, a failed monsoon) does not drag the whole picture.
We publish the sample size next to the numbers because it matters. Rain and temperature normals rest on eleven years; wave and rough-sea figures rest on four, because the marine model only goes back to 2022-01. Four years is enough to see the seasonal shape and not enough to trust a single day's difference between two months. Where a figure would rest on nothing, the cell says so instead of showing a plausible number.
Three columns describe rain, and they answer three different questions. Millimetres per month is total volume: how much water fell. Rain days is how many days had any measurable rain — including a ten-minute shower at four in the afternoon, which is why even February shows several. Heavy-rain days is the number of days with a genuinely wet total, the kind that cancels a boat trip or floods the road to the beach; that is the column to watch if you are deciding between two months in the green season.
Read together, the pattern is clear. From November to March rain is light and brief. April is warm and humid with the first afternoon storms. From May the south-west monsoon settles in and the monthly totals triple; May and October are the wettest months by volume, September and October have the most heavy-rain days. November is still wet on the west coast but the sea has already calmed, and by December the totals halve again.
Rain is inconvenient; the sea is the real seasonal difference on Phuket. From May to October the south-west monsoon pushes a swell onto the west-coast beaches — Patong, Karon, Kata, Kamala, Surin, Bang Tao, Nai Thon, Mai Khao — and lifeguards raise red flags on the rough days. The 'rough-sea days' column counts the days in a median month when the modelled maximum wave height crosses the threshold at which swimming becomes dangerous at an exposed beach. July is the peak, with 13 such days in a median month; from November to April the count is zero.
This is also why the east and south coasts matter in the green season. Chalong, Panwa, Rawai and the eastern side face Phang Nga Bay, sheltered from the monsoon swell; the water there is flat when Patong is red-flagged, though the beaches are smaller and the water less clear. If you are coming between June and September and want to swim every day, the area you choose matters more than the month.
Phuket sits eight degrees north of the equator, and the temperature table shows it: median daily highs span only 28.7–31.7 °C across the whole year and nights stay between 24.1 and 25.9 °C. March is the hottest month, and the humidity numbers — mid-seventies in the dry season, mid-eighties in the wet — explain why April feels harder than the thermometer suggests.
Sunshine follows the rain in mirror image: March has the most (343 hours in a median month, about 11.4 a day), September the least (248 hours, still 8.3 a day). Even the dullest month of the green season has more daily sunshine than a northern European summer, which is the honest case for travelling then: cheaper rooms, empty beaches, a couple of rain bursts a day and a sea you have to be careful with.
For beaches and boat trips with the least uncertainty: December to March. February is the driest, the sea is flat everywhere, and the price for that certainty is the highest hotel rates of the year and the busiest beaches. If you want the dry season without the peak, late November and March are the edges — still dry and calm, with rates already sliding.
For value: May–June and September–October, in that order of comfort. Monthly rain is high, but heavy-rain days stay in single figures until September, and the rough-sea count in May is a third of July's. Book on the east or south coast if daily swimming is the point. For long stays — a month or a season — the calculus changes again: a villa month in the green season is markedly cheaper, the rain is a daily interlude rather than a holiday-wrecker, and the island is quiet. The price side of that decision lives in the index; this page only settles the weather.
February, with 21 mm of rain in a median month over 2015–2025. January and March are close behind; together with December these are the months with the fewest rain days.
May, with 343 mm in a median month. October is nearly as wet by volume, and September–October have the most heavy-rain days of the year.
From November to April a median month has no rough-sea days at all. The swell builds from May, peaks in July (13 rough days in a median month) and drops away in October. East- and south-coast beaches stay flat year-round because they face Phang Nga Bay.
Usually not. Monthly totals of 288 mm arrive mostly as bursts of an hour or two, often in the afternoon or overnight. A green-season month has 25 days with some rain, but only 4 days with heavy rain in a median month.
March, with a median daily high of 31.7 °C. The spread across the year is small — highs stay between 28.7 and 31.7 °C — but April combines the heat with rising humidity, so it feels the hottest.
It is the wettest month by volume (340 mm) but the sea is already calming — 2 rough-sea days in a median month against 13 in July — and rates are at their lowest. Good value if you accept daily showers; poor for boat trips.
Weather-wise, November to February: dry, calm, not yet at April's heat. For price, the green season: villa monthly rates fall and the island is quiet. The trade-off is roughly rain and swell against a lower rent; the index pages give the rent side.
Open-Meteo (ERA5), 2015–2026: a weather reanalysis for a west-coast grid point, monthly aggregates from 2015 to 2025, plus a marine model for wave height from 2022-01. We publish medians per calendar month with the number of years behind each figure, and refresh the file monthly.
Weather: Open-Meteo (ERA5), 2015–2026, licensed CC BY 4.0, grid point 7.89°N 98.30°E. Waves: Open-Meteo marine model, from 2022-01. Normals are medians of the monthly values for 2015–2025; the 'last twelve months' table uses the raw monthly values. Rough-sea days are days whose modelled maximum wave height exceeds the pipeline's swimming-safety threshold. Nothing is interpolated: an empty cell means no observation.