What Actually Impacts UV Radiation Levels?

Many of us assume that we can only be damaged by UV radiation when it is sunny and hot outside. This is far from true.

Although there are many factors that affect the intensity of the sun’s rays, damage can occur even on the coldest and cloudiest days. For this reason, it is important to understand what impacts UV levels so that you can be best prepared and protected.

UV radiation is impacted by:

UV radiation through clouds.


Cloud Cover

When it comes to sun exposure, cloud cover can be a double-edged sword. Thick, unbroken clouds can absorb and reflect certain UV rays and reduce their intensity. But, the sides of clouds can also magnify UV radiation back down to the earth’s surface and increase the amount we are exposed to. Clouds also do little to prevent UVA rays from reaching the earth’s surface.

UV radiation through air pollution.


Air Pollution

Urban smog, smoke, and other such forms of air pollution can reduce the intensity of UV radiation. The particles that make up air pollution can absorb or reflect UV rays back out of the atmosphere. However, there are many health risks associated with air pollution and you should limit your exposure to it regardless of the UV index.

UV radiation at high elevation.


UV radiation is much more intense at higher altitudes than it is at sea level. This is because the atmosphere is thinner at higher elevations and has fewer particles in it that can absorb or reflect the sun’s harsh rays. This is also why it is crucial to wear sun protection while skiing or doing any other such activities in the mountains.

Sunny beach in the tropics.


The most intense UV radiation occurs at the equator, where the sun is directly overhead. It reduces as you move away from the equator because the sun’s rays must go at an angle through the atmosphere. This causes rays to pass through many more particles in the air that absorb and reflect UV radiation.

Seasonal shift.

Time of Year

UV radiation changes throughout the year. The highest levels occur in the summer months, and the lowest levels in winter months. However, damaging rays from the sun are present throughout the year and protection should always be worn.

A great way to check how intense the sun’s rays are each day is to use your smartphone to check the current UV index.