Vitamin D in Vietnam in September: sun, UV and what to expect
Bad weather Bad weather: it rains on about 23 days in September (rainy or monsoon season), so sun is hard to count on and a beach stay is not recommended.
6.1 hsun window (UV 2.5+)
6.9peak UV Index
8 minto a full dose
30°Cafternoon high
23/30rainy days
22/30sunny days
How long in the sun in September?
- If you travel anyway, plan your sun session around midday (roughly 11:00 to 15:00), when the UV Index peaks at about 6.9. With about a quarter of your skin bare, a full dose takes around 8 minutes for skin type III at age 30, and about 14 minutes at age 65.
- Stop well before your skin turns pink. At this UV level skin type III can start to burn after about 29 minutes of midday sun, so cover up, find shade and use SPF 30+ on skin that stays out.
- On clear days the UV Index reaches about 8.4, which is very strong. Keep sessions short and protect the rest of the day.
- Water, sand and light surfaces reflect UV, so at the beach you get a little more sun than the number suggests, for the good and the bad.
| Skin type | Full dose, age 30 | Full dose, age 65 | Time to burn |
|---|---|---|---|
| Type I | 5 min | 10 min | 19 min |
| Type II | 6 min | 12 min | 24 min |
| Type III | 8 min | 14 min | 29 min |
| Type IV | 12 min | 22 min | 43 min |
| Type V | 15 min | 29 min | 58 min |
| Type VI | 26 min | 48 min | 97 min |
Minutes at midday for about 1,000 IU of vitamin D with a quarter of the body bare, at Hạ Long Bay, the median coastal place. Time to burn is the time to reach one minimal erythemal dose and does not depend on age. A rough planning guide, not medical advice.
Places in Vietnam in September
| Place | Rating | Sun window | Full dose | Afternoon high | Rainy days |
|---|---|---|---|---|---|
| Nha Trang | Bad weather | 7.7 h | 6 min | 32°C | 18/30 |
| Mũi Né | Bad weather | 7.8 h | 6 min | 31°C | 26/30 |
| Côn Đảo | Bad weather | 6.9 h | 7 min | 29°C | 26/30 |
| Hoi An | Bad weather | 6.8 h | 7 min | 32°C | 23/30 |
| Hạ Long Bay | Bad weather | 6.1 h | 8 min | 30°C | 23/30 |
| Da Nang | Bad weather | 7.0 h | 7 min | 32°C | 23/30 |
| Huế | Bad weather | 6.3 h | 8 min | 32°C | 22/30 |
| Ho Chi Minh City | Bad weather | 6.5 h | 7 min | 31°C | 29/30 |
| Phú Quốc | Bad weather | 6.3 h | 8 min | 29°C | 29/30 |
| Hanoi | Bad weather | 5.7 h | 8 min | 31°C | 23/30 |
Other months in Vietnam
- Jan Good
- Feb Excellent
- Mar Excellent
- Apr Excellent
- May Too hot
- Jun Too hot
- Jul Too hot
- Aug Too hot
- Sep Bad weather
- Oct Bad weather
- Nov Bad weather
- Dec Bad weather
Best months: January to April. Full Vietnam guide