Vitamin D in Guam in December: sun, UV and what to expect
Bad weather Bad weather: it rains on about 21 days in December (rainy or monsoon season), so sun is hard to count on and a beach stay is not recommended.
7.2 hsun window (UV 2.5+)
6.9peak UV Index
8 minto a full dose
31°Cafternoon high
21/30rainy days
29/30sunny days
How long in the sun in December?
- 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.
- 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 Ritidian Point, 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 December
| Place | Rating | Sun window | Full dose | Afternoon high | Rainy days |
|---|---|---|---|---|---|
| Tumon | Bad weather | 7.3 h | 8 min | 30°C | 21/30 |
| Two Lovers Point | Bad weather | 7.3 h | 8 min | 30°C | 21/30 |
| Ritidian Point | Bad weather | 7.2 h | 8 min | 31°C | 21/30 |
| Piti | Bad weather | 7.2 h | 8 min | 32°C | 20/30 |
| Hagåtña | Bad weather | 7.2 h | 8 min | 32°C | 20/30 |
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