UV index and sunburn time in Sapporo
UV peaks at 8.5 (very high) in July, around 11:30 local time. At that intensity, untanned skin of type III burns in about 27 min.
How long before you burn?
Sunburn after
27 min
unprotected, at peak UV in July
Peak UV index
8.5
Very high
With SPF 30
14 h
if applied properly and reapplied
UV index month by month
Peak value on a representative day of each month, with burn time for skin type III.
| Month | Peak UV | Category | Peak at | Burns after |
|---|---|---|---|---|
| January | 1.4 | Low | 11:30 | 164 min |
| February | 2.5 | Low | 11:30 | 93 min |
| March | 4.2 | Moderate | 11:30 | 56 min |
| April | 6.2 | High | 11:30 | 38 min |
| May | 7.7 | High | 11:30 | 30 min |
| June | 8.4 | Very high | 11:30 | 28 min |
| July | 8.5 | Very high | 11:30 | 27 min |
| August | 7.7 | High | 11:30 | 30 min |
| September | 5.9 | Moderate | 11:30 | 40 min |
| October | 3.6 | Moderate | 11:30 | 64 min |
| November | 1.9 | Low | 11:30 | 122 min |
| December | 1.2 | Low | 11:30 | 189 min |
Burn time by skin type
At peak UV in July, with no sunscreen.
| Fitzpatrick type | Description | Burns after |
|---|---|---|
| Type I | Always burns, never tans | 16 min |
| Type II | Burns easily, tans minimally | 20 min |
| Type III | Burns moderately, tans gradually | 27 min |
| Type IV | Burns minimally, tans well | 35 min |
| Type V | Rarely burns, tans profusely | 47 min |
| Type VI | Never burns, deeply pigmented | 78 min |
UV through the day
UV index by month and hour in Asia/Tokyo local time, daylight saving included. Darker cells mean stronger UV.
| Month | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Jan | 1 | 1 | 1 | 1 | 1 | |||||||||||||
| Feb | 1 | 1 | 2 | 3 | 2 | 2 | 1 | |||||||||||
| Mar | 1 | 1 | 3 | 4 | 4 | 4 | 3 | 2 | 1 | |||||||||
| Apr | 1 | 3 | 4 | 6 | 6 | 6 | 5 | 3 | 2 | 1 | ||||||||
| May | 1 | 2 | 4 | 6 | 7 | 8 | 7 | 6 | 4 | 2 | 1 | |||||||
| Jun | 1 | 3 | 5 | 6 | 8 | 8 | 8 | 7 | 5 | 3 | 1 | |||||||
| Jul | 1 | 3 | 4 | 6 | 8 | 9 | 8 | 7 | 5 | 3 | 2 | |||||||
| Aug | 1 | 2 | 4 | 6 | 7 | 8 | 7 | 6 | 4 | 2 | 1 | |||||||
| Sep | 1 | 3 | 4 | 5 | 6 | 5 | 4 | 3 | 1 | |||||||||
| Oct | 1 | 2 | 3 | 3 | 4 | 3 | 2 | 1 | ||||||||||
| Nov | 1 | 1 | 2 | 2 | 2 | 1 | ||||||||||||
| Dec | 1 | 1 | 1 | 1 | 1 |
none strongest
Other cities in Japan
Assumptions
- Clear sky. These are upper bounds. Cloud reduces UV, though less than people expect — you can burn on an overcast day.
- No reflection. Snow roughly doubles your effective dose, and water and sand both add to it. None of that is modelled here.
- Burn times are indicative. Published minimal erythemal doses vary by around 30% between studies, and individuals within a skin type vary more.
- SPF assumes proper application. Most people apply a quarter of the amount used in testing, so real protection is far lower than the label.