Best Time to Dive in Koh Tao
Plan for February to June, when the downpours ease — 3 days a month of heavy rain instead of 6. The marine life holds steady all year, so the weather picks the month. The wider season runs January to June.
- Best time
- Feb–Jun
- Water
- 28–31 °C
- Visibility
- 10–30 m
- Season runs
- Jan–Jun
- Dived from
- day boat and shore diving
- Tidal range
- 0.6–1.8 m
- Species logged
- 6
Where it is
111 km across · coastline from Natural Earth 10m
Diving in Koh Tao — monthly breakdown
A year of scuba diving conditions at a glance. Hover a month to isolate it.
| January | February | March | April | May | June | July | August | September | October | November | December | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Conditions | Good | Excellent | Excellent | Good | Good | Good | Moderate | Moderate | Poor | Poor | Poor | Poor |
| Water temp (°C) | 28 | 28 | 29 | 30 | 31 | 30 | 30 | 30 | 29 | 29 | 29 | 28 |
| Visibility (m) | 15–25 | 15–25 | 15–25 | 15–25 | 15–25 | 15–25 | 20–30 | 20–30 | 15–25 | 15–25 | 15–25 | 10–20 |
| Marine life | Peak | Peak | Peak | Peak | Peak | Peak | Peak | Peak | Peak | Peak | Peak | Peak |
| Best time | Peak | Peak | Peak | Peak | Peak |
Long-term averages, 2016–2025. Visibility is estimated from satellite chlorophyll-a. Water temperature is the surface mean; it is cooler at depth.
The Koh Tao diving season
January to June · Peak season
6 months- Water temperature
- 28–31 °C
- Visibility
- 15–25 m
- Rain
- 12 days a month
Diving conditionsSeas are usually flat. The wind eases. It rains less.
Marine lifeWhale shark (near-guaranteed) peaks at Koh Tao in these months.
July to August · Shoulder season
2 months- Water temperature
- 30–30 °C
- Visibility
- 20–30 m
- Rain
- 22 days a month
Diving conditionsThis is the wet season topside. The wind is up. The sea is calmer.
Marine lifeWhale shark (near-guaranteed) peaks at Koh Tao in these months.
September to December · Off season
4 months- Water temperature
- 28–29 °C
- Visibility
- 15–25 m
- Rain
- 21 days a month
Diving conditionsThis is the wet season topside. The sea is rougher. The wind is up.
Marine lifeWhale shark (near-guaranteed) peaks at Koh Tao in these months.
- Spring tides run 1.8 m against 0.6 m on neaps, so currents build around the full and new moon.
- Water temperature is satellite sea-surface temperature, so expect it cooler below the thermocline.
- Visibility is estimated from satellite chlorophyll-a.
Koh Tao water temperature and weather
333 underwater observation records · 25 surveyed years of ocean data · 10 years of sea temperature
Water & weather
Koh Tao water temperature by month
The dashed line is the monthly average. Eight days in ten fall inside the band.
10th to 90th percentile rangemonthly mean
Seas top 1.5 m on 3% of days. Enough to cancel a day boat
Gusts over 40 km/h, about where a day boat stays in port
4 of them bring heavy rain
| Month | Swell | Gusts over 40 km/h | Wet days | Heavy rain | Air | Daylight |
|---|---|---|---|---|---|---|
| January | 1.4 m | 6% | 8 | 1 | 28 °C | 11.5 h |
| February | 1.0 m | 1% | 8 | 1 | 28 °C | 11.7 h |
| March | 0.7 m | 0% | 6 | 1 | 29 °C | 11.9 h |
| April | 0.6 m | 0% | 11 | 3 | 30 °C | 12.2 h |
| May | 0.7 m | 1% | 22 | 5 | 30 °C | 12.5 h |
| June | 0.7 m | 0% | 20 | 4 | 30 °C | 12.6 h |
| July | 0.8 m | 2% | 22 | 5 | 29 °C | 12.5 h |
| August | 0.8 m | 1% | 21 | 4 | 29 °C | 12.3 h |
| September | 0.8 m | 1% | 23 | 6 | 29 °C | 12.1 h |
| October | 0.7 m | 0% | 26 | 11 | 29 °C | 11.8 h |
| November | 1.5 m | 7% | 22 | 8 | 28 °C | 11.5 h |
| December | 1.5 m | 7% | 13 | 5 | 28 °C | 11.4 h |
Swell is the rough end of the month: nine days in ten come in under it. Sea temperature covers 10 years, waves 4.
Pick your week
48 weeks from the daily record. Darker is better, against this site's own year. Pick a month for the detail.
| Week 1 | January week 1: Moderate | February week 1: Excellent | March week 1: Excellent | April week 1: Good | May week 1: Good | June week 1: Good | July week 1: Good | August week 1: Moderate | September week 1: Poor | October week 1: Poor | November week 1: Moderate | December week 1: Poor |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Week 2 | January week 2: Good | February week 2: Excellent | March week 2: Excellent | April week 2: Good | May week 2: Good | June week 2: Good | July week 2: Moderate | August week 2: Moderate | September week 2: Poor | October week 2: Poor | November week 2: Poor | December week 2: Poor |
| Week 3 | January week 3: Good | February week 3: Good | March week 3: Excellent | April week 3: Excellent | May week 3: Good | June week 3: Good | July week 3: Poor | August week 3: Good | September week 3: Poor | October week 3: Poor | November week 3: Poor | December week 3: Poor |
| Week 4 | January week 4: Moderate | February week 4: Good | March week 4: Good | April week 4: Good | May week 4: Moderate | June week 4: Good | July week 4: Poor | August week 4: Moderate | September week 4: Moderate | October week 4: Poor | November week 4: Poor | December week 4: Moderate |
January, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Moderate | 28 °C | 1.3 m | 26 km/h | 24% |
| Week 2 | Good | 28 °C | 1.5 m | 21 km/h | 21% |
| Week 3 | Good | 28 °C | 1.3 m | 21 km/h | 27% |
| Week 4 | Moderate | 28 °C | 1.2 m | 21 km/h | 31% |
February, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 28 °C | 0.9 m | 21 km/h | 24% |
| Week 2 | Excellent | 28 °C | 0.8 m | 22 km/h | 21% |
| Week 3 | Good | 28 °C | 1.1 m | 22 km/h | 28% |
| Week 4 | Good | 28 °C | 1.2 m | 22 km/h | 29% |
March, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Excellent | 29 °C | 1.0 m | 21 km/h | 20% |
| Week 2 | Excellent | 29 °C | 0.7 m | 21 km/h | 16% |
| Week 3 | Excellent | 29 °C | 0.7 m | 21 km/h | 20% |
| Week 4 | Good | 29 °C | 0.8 m | 20 km/h | 27% |
April, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 30 °C | 0.9 m | 20 km/h | 33% |
| Week 2 | Good | 30 °C | 0.7 m | 20 km/h | 34% |
| Week 3 | Excellent | 30 °C | 0.5 m | 20 km/h | 31% |
| Week 4 | Good | 31 °C | 0.4 m | 19 km/h | 43% |
May, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 31 °C | 0.6 m | 20 km/h | 58% |
| Week 2 | Good | 31 °C | 0.7 m | 20 km/h | 64% |
| Week 3 | Good | 31 °C | 0.7 m | 22 km/h | 73% |
| Week 4 | Moderate | 30 °C | 0.7 m | 25 km/h | 79% |
June, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 30 °C | 0.7 m | 26 km/h | 75% |
| Week 2 | Good | 30 °C | 0.7 m | 27 km/h | 61% |
| Week 3 | Good | 30 °C | 0.7 m | 26 km/h | 61% |
| Week 4 | Good | 30 °C | 0.8 m | 26 km/h | 71% |
July, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Good | 30 °C | 0.7 m | 26 km/h | 74% |
| Week 2 | Moderate | 30 °C | 0.9 m | 28 km/h | 77% |
| Week 3 | Poor | 30 °C | 0.9 m | 29 km/h | 72% |
| Week 4 | Poor | 30 °C | 0.8 m | 30 km/h | 69% |
August, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Moderate | 30 °C | 0.7 m | 30 km/h | 69% |
| Week 2 | Moderate | 29 °C | 0.7 m | 29 km/h | 64% |
| Week 3 | Good | 30 °C | 0.8 m | 27 km/h | 65% |
| Week 4 | Moderate | 30 °C | 0.8 m | 27 km/h | 75% |
September, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 29 °C | 0.9 m | 27 km/h | 79% |
| Week 2 | Poor | 29 °C | 0.8 m | 28 km/h | 75% |
| Week 3 | Poor | 29 °C | 0.8 m | 28 km/h | 75% |
| Week 4 | Moderate | 29 °C | 0.8 m | 26 km/h | 79% |
October, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 29 °C | 0.7 m | 23 km/h | 85% |
| Week 2 | Poor | 29 °C | 0.6 m | 22 km/h | 87% |
| Week 3 | Poor | 29 °C | 0.7 m | 21 km/h | 84% |
| Week 4 | Poor | 29 °C | 0.8 m | 22 km/h | 82% |
November, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Moderate | 29 °C | 0.8 m | 23 km/h | 84% |
| Week 2 | Poor | 29 °C | 1.1 m | 23 km/h | 75% |
| Week 3 | Poor | 29 °C | 1.6 m | 23 km/h | 66% |
| Week 4 | Poor | 29 °C | 1.9 m | 27 km/h | 65% |
December, week by week
| Week | Conditions | Water | Swell | Wind | Rain chance |
|---|---|---|---|---|---|
| Week 1 | Poor | 28 °C | 1.4 m | 29 km/h | 60% |
| Week 2 | Poor | 28 °C | 1.5 m | 27 km/h | 48% |
| Week 3 | Poor | 28 °C | 1.9 m | 27 km/h | 35% |
| Week 4 | Moderate | 28 °C | 1.6 m | 27 km/h | 29% |
10 years of daily records, averaged into weeks.
Gear & storms
What to wear
Off the coldest water of each month, not the average — that is what the suit has to cope with.
| January | February | March | April | May | June | July | August | September | October | November | December | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Suit | January: skin | February: skin | March: skin | April: skin | May: skin | June: skin | July: skin | August: skin | September: skin | October: skin | November: skin | December: skin |
One suit covers the whole year: a skin or 3 mm shorty.
Swell through the year
The rough end of each month — nine days in ten come in under it.
Amber is over 1.5 m.
Tides
Tropical storms
1 of the last 30 Januarys saw a tropical storm pass within 250 km. Anything has been recorded Jan, Nov.
Share of the last 30 years with a storm that month.
- NOAASea surface temperature, from OISST and MUR
- ERA5Wind, waves, rain and air temperature, via Open-Meteo
- OBISMarine species records within 60 km
- IBTrACSTropical cyclone tracks, 1996 to 2025
Koh Tao marine life — what you'll see diving
| Species | When | Observed window | Reliability | Evidence | Records |
|---|---|---|---|---|---|
| Whale shark | All year | Near-guaranteed | 106 | ||
| Bluespotted ribbontail ray | All year | Likely | 51 | ||
| Green turtle | All year | Likely | 72 | ||
| Blacktip reef shark | All year | Likely | 49 | ||
| Bigeye trevally | Feb, Apr, Nov | Hit-or-miss | 20 | ||
| Hawksbill turtle | Apr–Jun, Sep | Hit-or-miss | 16 |
- Observed window
- Months with records. Peak is where most of them fall.
- Reliability
- Near-guaranteed in 60% of surveyed years or more
- Likely 30% to 60%
- Hit-or-miss under 30%
- Evidence
- Years it was seen, out of the years anyone surveyed.
- Records
- OBIS sightings within 60 km.
These are sightings people logged, not a full survey of the reef. A species missing from a month may just mean nobody recorded one.
Diving Koh Tao — common questions
- When is the best time to dive Koh Tao?
- Plan for February to June, when the downpours ease — 3 days a month of heavy rain instead of 6. The marine life holds steady all year, so the weather picks the month. The wider season runs January to June.
- When is the diving season in Koh Tao?
- The diving season in Koh Tao runs January to June, and it is at its best February to June.
- Is the diving in Koh Tao good for beginners?
- Yes. It suits Open Water divers, so it works for a first trip after certification.
- How warm is the water in Koh Tao?
- Between 28 and 31 °C at the surface across the year, coldest in January and warmest in May. It runs cooler below the thermocline.
- What wetsuit do I need in Koh Tao?
- A skin or 3 mm shorty covers the coldest water of the year. The same suit works all year.
- What is the visibility like in Koh Tao?
- Roughly 10 to 30 m depending on the month. That is estimated from satellite chlorophyll-a rather than measured in the water.
- What will I see diving Koh Tao?
- The most consistently recorded species are Whale shark (near-guaranteed), Bluespotted ribbontail ray (likely) and Green turtle (likely), from 333 records within 60 km.
- Does Koh Tao get tropical storms?
- Yes. Over 30 years of records a storm passed within 250 km in Jan, Nov, most often in January at 1 of 30 years.
- Is there current in Koh Tao?
- The tide rises and falls 1.8 m around the full and new moon, against 0.6 m in between. How much of that becomes current depends on the shape of the channel.
- When should I avoid Koh Tao?
- October–November are the weakest months for conditions.
- How do you dive Koh Tao?
- Mostly from day boats and the shore. Trips run through the season, Jan–Jun.