Vitamin D in Guam in September: sun, UV and what to expect
Bad weather Bad weather: September is a peak month for tropical storms here, so a beach stay is not recommended. If you still go, check forecasts and travel insurance.
7.0 hsun window (UV 2.5+)
7.8peak UV Index
7 minto a full dose
30°Cafternoon high
27/30rainy days
23/30sunny 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 7.8. With about a quarter of your skin bare, a full dose takes around 7 minutes for skin type III at age 30, and about 13 minutes at age 65.
- Stop well before your skin turns pink. At this UV level skin type III can start to burn after about 26 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 9.1, 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 | 9 min | 17 min |
| Type II | 6 min | 11 min | 21 min |
| Type III | 7 min | 13 min | 26 min |
| Type IV | 10 min | 19 min | 38 min |
| Type V | 14 min | 26 min | 51 min |
| Type VI | 23 min | 43 min | 85 min |
Minutes at midday for about 1,000 IU of vitamin D with a quarter of the body bare, at Hagåtña, 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 Guam in September
| Place | Rating | Sun window | Full dose | Afternoon high | Rainy days |
|---|---|---|---|---|---|
| Tumon | Bad weather | 7.4 h | 7 min | 30°C | 30/30 |
| Two Lovers Point | Bad weather | 7.4 h | 7 min | 30°C | 30/30 |
| Hagåtña | Bad weather | 7.0 h | 7 min | 30°C | 27/30 |
| Ritidian Point | Bad weather | 7.0 h | 7 min | 30°C | 29/30 |
| Piti | Bad weather | 6.8 h | 7 min | 30°C | 27/30 |
Other months in Guam
- Jan Excellent
- Feb Bad weather
- Mar Bad weather
- Apr Bad weather
- May Bad weather
- Jun Bad weather
- Jul Bad weather
- Aug Bad weather
- Sep Bad weather
- Oct Bad weather
- Nov Bad weather
- Dec Bad weather
Best months: January. Full Guam guide