UV Index

UV Index ThermometerYou may have heard: “The sun’s UV rays are the strongest during peak times of 10am to 4pm.” But how is that determined? This saying actually references the UV Index, a tool that predicts the ultraviolet radiation levels on a 1 – 11+ point scale, giving you more information to determine what sun safe behaviors are needed to stay protected.

What is the UV Index?

The UV Index provides a daily forecast of the expected risk of overexposure to the sun. The Index predicts UV intensity levels on a scale of 1 to 11+, where 1 indicates a minimal risk of overexposure and 11+ means a very high risk. The UV Index takes into consideration location, elevation, time of day, local weather conditions, and even cloud coverage to estimate the level of UV radiation that is likely to reach the ground. The UV Index provides useful information that can help you plan for outdoor activities, such as should you wear a hat? UPF clothing? Etc.

How can the UV Index be used?

The UV Index provides actionable information that can help you plan your day and minimize exposure to ultraviolet radiation. 

For example, because the UV Index is highest between 1pm and 3pm, if you chose to mow your lawn or go to the pool at mid-day, you could be exposed to extreme levels of ultraviolet radiation. Waiting just a few hours, can dramatically minimize your exposure. 

What are the ‘levels’ of the UV Index?

UV Index ranges from 1 to 11+. The higher the number, the more UV radiation you will be exposed to. When the UV Index is close to 11+, you should be extra vigilant about your sun safety habits. Below, find the UV Index and the corresponding level of ultraviolet radiation exposure.

UV Index Sun Safety Melanoma Prevention

You must be especially cautious when the UV Index is anywhere from High to Extreme. Between this range, it’s possible to burn within minutes of unprotected sun exposure. 

How do I know the UV Index for my area?

The U.S. Environmental Protection Agency (EPA) provides a free tool to look up your community’s UV Index. The EPA has also created a free, downloadable app compatible with both iOS and Android devices - download it here. Some smartphone weather apps also include this helpful information.

Does that mean I don’t have to wear sunscreen or UPF clothing if it’s ‘off peak?’

No. You are constantly exposed to ultraviolet radiation when in the sun. Sun damage happens in the winter and when it’s cloudy. It’s important to remember that sun damage is cumulative – so even small amounts of exposure add up over time. UV rays also reflect off water, sand, and snow which can effectively double your exposure.

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