Many people think that sunscreen isn't necessary when the sky is overcast. This is actually a myth : even when it's cloudy, UV rays continue to affect the skin. Sunscreen is therefore essential year-round, not just in summer or on bright sunny days.  

The real culprits of sun damage are UV rays  

We commonly associate sun damage with summer heat . Actually , The heat we perceive comes mainly from infrared rays, which increase the temperature but are not the main cause of skin damage.  

Skin damage is mainly caused by:  

These rays are present year-round , regardless of the season. Therefore, sunscreen shouldn't be considered just a summer product.  

Why clouds don't really block UV rays  

Clouds are composed of water vapor and ice crystals. They can block some visible light, but they cannot completely block ultraviolet rays. The effect of clouds on UV radiation It depends on several factors , such as density , the thickness of the clouds and the angle of the sun .  

Clouds absorb only some UV radiation, but if they are thin or fragmented clouds, UV rays pass through and are reflected by the cloud surface . In some cases, cloud surfaces can even reflect UV rays, increasing the amount that reaches the skin. Studies indicate that up to 80% of UV rays can penetrate cloud cover.  

Clouds are not an effective shield against UV rays. Even when the sky is overcast, radiation can reach the skin and cause damage over time. This is why sun protection is important year-round . in winter, in the walks in the city and on all occasions when you are exposed to the sun, Not just on summer days or at the beach. Using it consistently is one of the simplest and most effective ways to protect your skin over the long term.  

Sources

WHO, NOAA