Vitamin D in Guam in January: sun, UV and what to expect
Excellent Excellent. The sun is strong for most of the day in Guam in January, so a full vitamin D dose takes only about 8 minutes at midday, and the usable window lasts 7.2 hours a day.
7.2 hsun window (UV 2.5+)
7.0peak UV Index
8 minto a full dose
29°Cafternoon high
16/30rainy days
27/30sunny days
Best places in Guam in January: Piti (excellent), Hagåtña (excellent), Tumon (excellent), Two Lovers Point (excellent).
How long in the sun in January?
- Plan your sun session around midday (roughly 11:00 to 15:00), when the UV Index peaks at about 7.0. 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 | 11 min | 21 min | 43 min |
| Type V | 15 min | 29 min | 57 min |
| Type VI | 25 min | 48 min | 95 min |
Minutes at midday for about 1,000 IU of vitamin D with a quarter of the body bare, at Tumon, 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 January
| Place | Rating | Sun window | Full dose | Afternoon high | Rainy days |
|---|---|---|---|---|---|
| Piti | Excellent | 7.3 h | 7 min | 30°C | 11/30 |
| Hagåtña | Excellent | 7.2 h | 8 min | 29°C | 11/30 |
| Tumon | Excellent | 7.2 h | 8 min | 29°C | 16/30 |
| Two Lovers Point | Excellent | 7.2 h | 8 min | 29°C | 16/30 |
| Ritidian Point | Bad weather | 7.2 h | 8 min | 29°C | 21/30 |
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