FAQ

What does UV Index mean?

UV Index is a standardized scale that estimates the strength of sunburn-producing ultraviolet radiation expected at the earth's surface, with emphasis on UVB and the portion of UVA that contributes to skin damage. In practical terms, it turns complex atmospheric conditions into a single number that reflects how intense the sun's UV is likely to feel.

The calculation depends on factors such as the sun angle, ozone, clouds, elevation, and other atmospheric inputs. Higher numbers mean stronger ultraviolet radiation and a greater potential for skin and eye exposure in less time.

Is this live sensor data?

No. The pages on UVIndexToday.app are based on NOAA forecast data rather than a live UV sensor at every location. You can read more about the source on the Data page.

How often is the data updated?

NOAA updates the upstream UV forecast on a daily cycle. When a new forecast is published, values on UVIndexToday.app may change as the site refreshes its pages.

Why does a page sometimes differ from what I expected outdoors?

UV forecasts are area-based estimates. Real conditions at your exact location can vary because of shifting cloud cover, wildfire smoke, haze, altitude, nearby water, snow, sand, buildings, trees, and whether you are in direct sun or shade.

Why is the number for my town similar to nearby places?

Many nearby places share similar forecast conditions because they fall within the same broader weather pattern and forecast grid area. Differences become more likely across larger distances, major elevation changes, coastal transitions, or distinct regional weather setups.

What do the labels low, moderate, high, very high, and extreme mean?

Those labels are category names attached to ranges on the UV Index scale, based on standard EPA UV Index guidance. They provide quicker shorthand than the raw number alone and make it easier to compare conditions at a glance.

Is UVIndexToday.app affiliated with NOAA or another government agency?

No. UVIndexToday.app is an independent site that uses publicly available forecast data, but it is not affiliated with NOAA or any other government agency.

It is a separate site that repackages that information into easier-to-browse location pages.

What should I do if I think a page is wrong?

If you believe a page contains an incorrect location, misleading wording, or a presentation problem, use the Contact page and include the page URL, the place you were viewing, and a short description of the issue.