Phuket or Koh Samui in July?
On climate data, Koh Samui comes out ahead overall in July. See the per-criterion details below.
PhuketPhoto: PavF · CC BY-SA 3.0
Koh SamuiPhoto: Sonia Selivonchik · CC BY-SA 4.0Key figures in July
| Criterion | Phuket | Koh Samui |
|---|---|---|
| Day | 28 °C | 29 °C ★ |
| Night | 27 °C | 28 °C ★ |
| Sea | 29 °C | 30 °C ★ |
| Rainy days | 16 rainy days | 8 rainy days ★ |
| Sun | 6 h/day | 6 h/day ★ |
Winner by travel type
Trade-offs
- Koh Samui is drier, with about 8 fewer rainy days.
Phuket or Koh Samui in July: the short answer
In July, Koh Samui comes out ahead on the overall climate score (Phuket 63/100 vs Koh Samui 74/100). That is a snapshot of one month, though — which one truly fits depends on what you want from the trip, so the breakdown below goes criterion by criterion.
Across the whole year Phuket averages a climate score of 69/100, Koh Samui 73/100. Both profiles below are historical monthly averages, not a forecast.
Weather in July, side by side
By day, Phuket sits near 28 °C and Koh Samui near 29 °C — warmer in Koh Samui. At night it is roughly 27 °C versus 28 °C.
On rain, Phuket sees about 16 rainy days in July and Koh Samui about 8 — drier in Koh Samui. Koh Samui gets more sunshine (6 vs 6 hours a day).
Sea temperature and swimming
In July the water is about 29 °C at Phuket and 30 °C at Koh Samui — warmer for swimming at Koh Samui. Over the year, Phuket is comfortable for swimming (from ~21 °C) in January, February, March, April, May, June, July, August, September, October, November and December, Koh Samui in January, February, March, April, May, June, July, August, September, October, November and December. Peak sea warmth is May for Phuket and May for Koh Samui.
Rain and sun across the year
Over a full year Phuket records roughly 142 rainy days and Koh Samui about 118 — the drier of the two overall is Koh Samui. At their sunniest, Phuket reaches about 8 hours of sun a day (March) and Koh Samui about 8 (March). If dependable dry, sunny weather is your top priority, weigh these annual totals alongside the single month above.
Best time to visit each
Climatically, Phuket is at its best in January, February, March and December, while Koh Samui peaks in January, February, March and July. If your dates are fixed, pick the destination whose strong season overlaps them; if you are flexible, plan around these windows.
Which suits which kind of trip
Based on the July scores for each travel style:
Beach & swimming: Koh Samui scores higher in July.
City breaks: Koh Samui scores higher in July.
Active & hiking: Koh Samui scores higher in July.
Family: Koh Samui scores higher in July.
Verdict: which should you pick?
There is no single winner — it depends on your month and your priority. For July specifically, use the head-to-head above; over the year, Koh Samui carries the slightly higher overall climate score. Choose Phuket if its strong months and profile match your plan, Koh Samui if its do. The month-by-month pages for each destination give you the full picture before you book.