FIND OUT HOW DANGEROUS THE SUN CAN BE

UV radiations are more intense during the hottest hours of the day and in very warm places. Sun intensity also depends on clouds and pollution.

What time is it? At midday, UV radiations can be 8 or 9 times stronger than at 9 in the morning, and three times stronger than at 10 in the morning. It is easy to follow this rule: If our shadow is shorter than our height then the sun is at peak time and radiations very intense.

What day is it? The sun is more intense towards the end of spring and in midsummer; it reaches its maximum during the summer solstice of (the beginning of summer is warmer but not due to radiations but rather because the Earth is warmer).

Where am I? UV radiations get more intense the closer we get to the equator (because sunrays hit the earth perpendicularly) and the farther we go away from sea level (because the atmosphere is thinner there). Radiations increase 10-12% for every 1.000 meters that we rise.
Radiations get to us even when under water, about 40% at a depth of half a meter. The magnifying glass effect that is created by drops of water when we get wet is not very important.

What is the weather like? Clouds do filter radiations. They filter more radiations when they are low and dense. However, depending on the shape, they can disperse and reflect radiations so that they arrive in parts of the body that normally are not exposed. More on this topic can be found in the Guide. Pollution (contaminated particles in the air) can also filter and reflect UV rays but at a smaller scale.

Radiations get to not only the exposed part of our bodies but also to those parts that are perpendicular to the sun. Rays get to us directly but are also reflected and get to us from different directions and thus we have to protect all parts of our body such as the side of our faces and eyes.

Rays bounce mainly on the surfaces (floor, walls...). Fresh snow can reflect 80% of UV rays, so that we get almost double the radiations we would get if snow did not reflect them. At a winter day we could get more radiations than we would at summer day and all over our body. Apart from the snow, the following surfaces can reflect rays: cement, fresh concrete (55%) and dry sand (40%).

Only reflected rays get to us when we are in the shadow (diffused radiation). The larger and denser the shadow is, the smaller the amount of reflected rays that gets to us. For example, in a house with windows, only 10% of UV radiations get to us whereas under a sun umbrella in a clear day, the amount increases to 40%.