UV INDEX
The intensity of the sun's UV rays reaching the earth's surface varies by latitude, date, time of day, altitude, ozone and cloud cover. For simplicity, various UV indexes have been developed and one is now standardised by the World Health Organisation (WHO).
The UVI gives an indication of the level of UV radiation and the potential danger of sun exposure.
UV radiation is reflected or scattered to varying degrees by different surfaces: e.g. snow can reflect as much as 80% of UV radiation, dry beach sand about 15%, and sea foam about 25%.
In reporting the UVI, most emphasis is placed on the maximum UV level on a given day. This occurs during the four-hour period around solar noon.
| UVI | Colour Code | Level | Description |
|---|---|---|---|
| <3 | Green | Low | Low danger for the average person. |
| 3-6 | Yellow | Moderate | Moderate risk, stay in shade at noon. Apply sunscreen even if cloudy. |
| 6-8 | Orange | High | Risk of harm, protection needed. Reduce time in sun between 11am to 5pm. |
| 8-11 | Red | Very High | Very high risk of harm. Minimise sun exposure between 11am to 5pm. |
| 11+ | Violet | Extreme | Avoid sun exposure between 11am and 6pm. |
The solar noon in Andalucía is deceptively late: about 13.20 hrs in winter and 14.20 hrs in summer. This is due to Andalucía's longitude being west of Greenwich and Spain being in Central European Time.
More precisely, solar noon is 14.06 hrs in eastern Almería, 14.20 hrs in Marbella and 14.30 hrs on the Huelva-Portugal border.
Expected maximum values of UV index, based on historical data for Andalucía, are.
| Month | Málaga | Cádiz and Granada |
|---|---|---|
| Jan | 1.5 - 2 | 1.5 - 2 |
| Feb | 2 - 3.5 | 2 - 3.5 |
| Mar | 3.5 - 5 | 3.5 - 5.5 |
| Apr | 5 - 6.5 | 5 - 7 |
| May | 8 | 8.5 |
| Jun | 8 | 8.5 - 9 |
| Jul | 8 | 9 |
| Aug | 8 - 6.5 | 8.5 - 7 |
| Sep | 7 - 5.5 | 7 - 5.5 |
| Oct | 5 - 3 | 5.5 - 3 |
| Nov | 3 - 1.5 | 3 - 1.5 |
| Dec | 1.5 | 1.5 |
(The two numbers represent the range from the beginning to the end of the month.)
At other times of the day it will be less. A maximum value of 9 at solar noon will be 7 two hours before or after solar noon, 5 three hours before and after solar noon, and 3 four hours before and after solar noon.
For Marbella, in summer when the solar noon is 14.20h the expected maximum UV index is published as 9.
| Time | UV Index |
|---|---|
| 10.20 | 3 |
| 11.20 | 5 |
| 12.20 | 7 |
| 13.20 | 8,5 |
| 14.20 | 9 |
| 15.20 | 8,5 |
| 16.20 | 7 |
| 17.20 | 5 |
| 18.20 | 3 |
These figure assume the receiving surface is flat and horizontal, taking in to account the incidence of the sun's angle. Be careful - If you are walking into or out of the late afternoon sun, the burning effect will be stronger than indicated in the table for the time of day.
Actual observations for Andalucía by AEMET (Spanish Met office)
Ultraviolet Radiation Forecast for next few days by AEMET (Spanish Met office)