UV index and sunburn time in Cardiff
UV peaks at 6.9 (high) in July, around 13:30 local time. At that intensity, untanned skin of type III burns in about 34 min.
How long before you burn?
Sunburn after
34 min
unprotected, at peak UV in July
Peak UV index
6.9
High
With SPF 30
17 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 | 0.6 | Low | 12:30 | 415 min |
| February | 1.3 | Low | 12:30 | 176 min |
| March | 2.7 | Low | 12:30 | 88 min |
| April | 4.5 | Moderate | 13:30 | 52 min |
| May | 6.0 | Moderate | 13:30 | 39 min |
| June | 6.8 | High | 13:30 | 34 min |
| July | 6.9 | High | 13:30 | 34 min |
| August | 5.9 | Moderate | 13:30 | 39 min |
| September | 4.0 | Moderate | 13:30 | 58 min |
| October | 2.1 | Low | 12:30 | 114 min |
| November | 0.8 | Low | 11:30 | 285 min |
| December | 0.4 | Low | 12:30 | 552 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 | 19 min |
| Type II | Burns easily, tans minimally | 24 min |
| Type III | Burns moderately, tans gradually | 34 min |
| Type IV | Burns minimally, tans well | 44 min |
| Type V | Rarely burns, tans profusely | 58 min |
| Type VI | Never burns, deeply pigmented | 97 min |
UV through the day
UV index by month and hour in Europe/London 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 | |||||||||||||||||
| Feb | 1 | 1 | 1 | 1 | 1 | |||||||||||||
| Mar | 1 | 1 | 2 | 2 | 3 | 2 | 2 | 1 | ||||||||||
| Apr | 1 | 2 | 3 | 4 | 4 | 4 | 4 | 3 | 2 | 1 | ||||||||
| May | 1 | 1 | 3 | 4 | 5 | 6 | 6 | 5 | 4 | 3 | 2 | 1 | ||||||
| Jun | 1 | 2 | 3 | 5 | 6 | 7 | 7 | 6 | 5 | 4 | 2 | 1 | ||||||
| Jul | 1 | 2 | 3 | 4 | 6 | 7 | 7 | 6 | 5 | 4 | 2 | 1 | ||||||
| Aug | 1 | 2 | 4 | 5 | 6 | 6 | 5 | 4 | 3 | 2 | 1 | |||||||
| Sep | 1 | 2 | 3 | 4 | 4 | 3 | 3 | 1 | 1 | |||||||||
| Oct | 1 | 2 | 2 | 2 | 2 | 1 | ||||||||||||
| Nov | 1 | 1 | 1 | 1 | ||||||||||||||
| Dec |
none strongest
Other cities in United Kingdom
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.