Best time to dive Koh Tao
Best February–May (the 'golden season', visibility often 25 m+); whale sharks mostly March–May with sightings again in September–October. November–December is the monsoon, with rain, wind and 5–10 m visibility.
Peak season: March–May, September
Overall diving, month by month
Balanced scoring · forecasts include the 2026/27 El Niño outlook
Confidence: Nov medium · Dec medium · Jan medium · Feb medium · Mar medium · Apr medium · May medium · Jun low · Jul low · Aug medium · Sep medium · Oct low · Nov low · Dec low
What's good when
Each attribute scored 0–10 for every month
| Nov2026 | Dec | Jan2027 | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Pelagic & big animals | 5 | 5 | 5 | 6 | 7 | 8 | 8 | 6 | 6 | 6 | 7 | 7 | 5 | 5 |
| Macro life | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 | 6 |
| Coral & reef health | 4 | 4 | 5 | 5 | 5 | 2 | 2 | 2 | 2 | 4 | 4 | 4 | 4 | 4 |
| Visibility | 3 | 3 | 6 | 7 | 7 | 7 | 7 | 6 | 6 | 6 | 6 | 5 | 3 | 3 |
| Water temperature | 10 | 10 | 10 | 10 | 10 | 9 | 9 | 9 | 10 | 10 | 10 | 10 | 10 | 10 |
| Weather & sea state | 5 | 5 | 7 | 8 | 9 | 9 | 8 | 8 | 8 | 8 | 8 | 7 | 5 | 5 |
| Operations & access | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 | 10 |
| Wreck diving | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
Climate outlook
How this year's forecast differs from a typical year
- Water temperature +0.8 °C · Gulf of Thailand runs hot in the spring after an El Niño (Nov 2026 – August 2027)
- Coral & reef health -1 · Reefs still recovering from post–El Niño bleaching (Nov 2026 – December 2027)
- Coral & reef health -2.1 · Post–El Niño bleaching risk, as in 2010 when all Koh Tao reefs bleached (Apr 2027 – July 2027)
Water temperature & visibility
| Month | Water | Visibility |
|---|---|---|
| November 2026 | 28.9 °C (84 °F) | 5–10 m |
| December 2026 | 28.5 °C (83 °F) | 5–12 m |
| January 2027 | 28.0 °C (82 °F) | 10–20 m |
| February 2027 | 28.2 °C (83 °F) | 15–25 m |
| March 2027 | 29.3 °C (85 °F) | 15–30 m |
| April 2027 | 30.3 °C (87 °F) | 15–30 m |
| May 2027 | 30.7 °C (87 °F) | 15–25 m |
| June 2027 | 30.1 °C (86 °F) | 15–20 m |
| July 2027 | 29.5 °C (85 °F) | 15–20 m |
| August 2027 | 29.3 °C (85 °F) | 15–20 m |
| September 2027 | 29.2 °C (85 °F) | 15–20 m |
| October 2027 | 29.1 °C (84 °F) | 8–15 m |
| November 2027 | 28.5 °C (83 °F) | 5–10 m |
| December 2027 | 27.9 °C (82 °F) | 5–12 m |
Marine life calendar
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| whale shark | ● | Peak | Peak | Peak | ● | ● | ● | |||||
| batfish | ● | ● | ● | ● | ● | ● | ● | ● | ● | ● | ● | ● |
| barracuda | ● | ● | ● | ● | ● | ● | ● | ● | ● | ● | ● | ● |
| blacktip reef shark | ● | ● | ● | ● | ● | ● | ● | ● | ● | ● | ● | ● |
| moray eels | ● | ● | ● | ● | ● | ● | ● | ● | ● | ● | ● | ● |
Peak = best odds · ● = regularly seen · blank = unlikely. Calendar months, every year.
About the diving
- Difficulty
- Beginner
- Current strength
- 2 / 5
- Luxury level
- 3 / 5
- Typical depth
- 5–25 m
- Max depth of interest
- 35 m
- Dive styles
- Day boat, Resort
- Suggested certification
- Open Water
- Nearest airport
- USM
- Snorkelling
- Good
- Known for
- whale shark, batfish, barracuda, blacktip reef shark
Famous sites: Chumphon Pinnacle · Sail Rock · Southwest Pinnacle · HTMS Sattakut
Season notes & sources
- Best February–May (the 'golden season', visibility often 25 m+); whale sharks mostly March–May with sightings again in September–October. November–December is the monsoon, with rain, wind and 5–10 m visibility.
- The 2009–10 El Niño pushed water to about 32–34 °C in May 2010 and bleached all of Koh Tao's reefs.
- Big Blue Diving documents local white-eyed morays, which generally shelter by day and hunt at night. Resident presence is not a monthly abundance peak.