What is the UV Index?
The ultraviolet index or UV Index is an international standard measurement of the strength of sunburn-producing ultraviolet (UV) radiation at a particular place and time that takes into account elevation, cloud coverage and time of day.
How do I find the UV index for my location?
Most smart phone weather applications will list the UV index. The UV index changes over the course of the day so it is important to check it regularly.
What is Ultra Violet Radiation?
UV radiation is the part of the light spectrum that reaches the earth from the sun. Its wavelengths are shorter than visible light making it invisible to the naked eye. These wavelengths are classified as UVA, UVB, or UVC. The UVC rays are the shortest and the majority are absorbed by the ozone layer and never reach earth. UV radiation is the main cause of non-melanoma skin cancers (basal cell carcinoma BCC and squamous cell carcinoma SCC). Melanoma causes are more complex but most experts believe, especially for fair skinned people, UV radiation plays a major role in melanoma development.
What are UVA rays?
UVA rays are considered the long wavelengths and although they are less intense than UVB, they are present with equal intensity during all daylight hours throughout the year and can penetrate clouds and glass. UVA rays penetrate the skin more deeply and have long been known to play a major part in tanning and photoaging (wrinkles and brown spots) and recently studies have proven UVA damages the skin cells called keratinocytes in the basal layer of the epidermis (which is where most skin cancers occur). Basal cells and squamous cells are types of keratinocytes. UVA is the primary emission of tanning beds and these high pressure lamps can emits doses 12 times stronger than the sun. People who use tanning beds are 2.5 times more likely to develop SCC and 1.5 times more likely to develop BCC. Tanning bed exposure also substantially increases melanoma risk.
What are UVB rays?
UVB are the short wavelength rays and the major cause of skin reddening and sunburn. It damages the skin’s more superficial epidermal layers. It plays a key role in the development of skin cancer and a contributing role in tanning and photoaging. It does not penetrate glass and its intensity varies by season, location and time of day. UVB rays can burn and damage the skin year round, especially at high altitudes and on reflective surfaces such a snow, sand, water and ice, which can bounce back up to 80% of the rays meaning they damage the skin twice.
Does the UV index matter on cloudy days?
YES! Up to 80% of the sun’s rays can penetrate on cloudy days.
How do you interpret the UV Index?
The UV index ranges from 0-11+.
0 to 2:Low and means you are in low danger from the UV rays for the average person. If you burn easily you should still wear 30+ SPF.
3to 5: Moderate and means moderate risk of harm from unprotected sun exposure. Stay in the shade near midday when sun is the strongest. If outdoors wear a hat and UV blocking sunglasses. Apply sunscreen SPF 30+ every 2 hours. Watch out for bright surfaces like, sand, water and snow which reflect UV and increase exposure.
6 to 7: High and means a high risk of harm from unprotected sun exposure. Protection for the skin and eyes is needed. You should reduce time in the sun between 10-4 pm. If outside seek shade and wear a hat, UV blocking sunglasses and SPF 30+ every 2 hours and after swimming or sweating. Watch out for bright surfaces like, sand, water and snow which reflect UV and increase exposure.
8 to 10: Very high and means very high risk of harm from unprotected sun exposure. Unprotected skin and eyes will be damaged and can burn quickly. You should reduce time in the sun between 10-4 pm. If outside seek shade and wear a hat, UV blocking sunglasses and SPF 30+ every 2 hours and after swimming or sweating. Watch out for bright surfaces like, sand, water and snow which reflect UV and increase exposure.
11 or more: Extremely high and extremely high risk of damage from unprotected sun exposure. Take all precautions because unprotected skin and eyes can burn in minutes. You should reduce time in the sun between 10-4 pm. If outside seek shade and wear a hat, UV blocking sunglasses and SPF 30+ every 2 hours and after swimming or sweating. Try to avoid bright surfaces like, sand, water and snow which reflect UV and increase exposure.
What is the Shadow Rule?
The shadow rule is an easy way to tell how much sun exposure you are getting. If your shadow is taller than you are, which is generally in the early morning or late afternoon, your UV exposure is likely to be lower. If your shadow is shorter than you are, which is usually around midday between 10am-2pm, you are being exposed to higher levels of UV radiation. Seek shade and protect you skin and eyes.
What is the UV Index?