About UV by Hour
UV by Hour is a free, independent site that shows the UV index hour by hour for any place, with plain-English guides to staying safe in the sun, especially outdoors and on the trail.
What you can do here
- See today’s UV curve for any place, with the hours when sun protection is recommended.
- Compare the next few days side by side.
- Read how elevation, snow and open terrain change your sun exposure at popular hiking destinations.
- Read the guides on the UV index, timing, and what to wear.
Where the data comes from
UV forecasts come from currentuvindex.com, a free service that says its UV index forecasts and real-time data come mainly from NOAA, the U.S. National Oceanic and Atmospheric Administration (see their data page). The data is licensed under CC BY 4.0. NOAA’s own UV index products are described at the Climate Prediction Center.
Place search uses OpenStreetMap. Time zones are worked out on your device, so no time zone service is involved.
How to read the chart
- The colours follow the standard UV index scale used by the WHO and the EPA: low, moderate, high, very high and extreme.
- The bracket at the top marks the hours when the index is 3 or higher, which is when the WHO recommends sun protection.
- The “now” marker shows the current value, and the peak label shows the highest value of the day.
- Levels are based on the index rounded to a whole number, as the official scale is.
What the site can’t tell you
- It’s a model forecast. Real UV can differ, especially when cloud is patchy or changing.
- It doesn’t resolve peaks and valleys. The forecast covers an area. Add roughly 10% to 12% for each 1,000 metres you climb above it.
- It only looks a few days ahead, about four days.
- The starting place is a guess. If you haven’t chosen a place, we estimate a nearby city from your connection. Use your location or search for an exact spot.
- It can’t account for you. Skin type, medicines and health conditions change how much protection you need.
How the guides are written
Our guides are plain-English summaries of guidance from organisations such as the World Health Organization, the U.S. EPA, NOAA, the American Academy of Dermatology, the Skin Cancer Foundation and the U.S. FDA. We link to our sources at the bottom of each guide, and we show when each page was last updated. Where sources differ, we say so. If you spot a mistake, please tell us.
Nothing on this site is medical advice. If you’re worried about your skin, see a doctor or dermatologist.
Independence
UV by Hour doesn’t currently run ads or recommend specific products. If that changes, we’ll say so clearly and label any sponsored or affiliate content.
Corrections and contact
Questions, corrections and data problems are welcome. See the contact page or email hello@uvbyhour.com.