Zionsville, Indiana
Zionsville UV index
The modeled UV index for Zionsville hour by hour, shown against the clear-sky ceiling the sky would reach with no cloud, with protection guidance, the days ahead, and the record so far.
UV in Zionsville
Wednesday, July 22, 2026Cloud is holding the peak to 5 of a possible 8.
Protection at today’s peak
Cover up. Hat, sunglasses, SPF 30, and shade around midday. Full guidance is on the EPA’s UV Index scale. Modeled on a roughly 40 km grid, so it describes Zionsville rather than your yard.
Tomorrow, hour by hour
Tomorrow’s modeled index against the clear-sky ceiling, Thursday, July 23. The whole day is forecast, so the whole curve is dashed and it will move as the model reruns. Hover or drag to read any hour.
The hours in figures
Today’s stored curve to one decimal, from an hour before sunrise to an hour after sunset. The overnight hours left out are zero.
| Hour | UV | Clear sky | Cloud | Category |
|---|---|---|---|---|
| 5 AM | 0.0 | 0.0 | 60% | Low |
| 6 AM | 0.0 | 0.0 | 84% | Low |
| 7 AM | 0.1 | 0.1 | 6% | Low |
| 8 AM | 0.5 | 0.5 | 1% | Low |
| 9 AM | 1.4 | 1.5 | 7% | Low |
| 10 AM | 3.1 | 3.2 | 5% | Moderate |
| 11 AM | 4.7 | 5.3 | 6% | Moderate |
| 12 PM | 4.0 | 7.4 | 1% | Moderate |
| 1 PM | 3.5 | 8.7 | 0% | Moderate |
| 2 PM | 4.6 | 8.9 | 0% | Moderate |
| 3 PM | 5.4 | 8.0 | 32% | Moderate |
| 4 PM | 3.9 | 6.1 | 100% | Moderate |
| 5 PM | 2.8 | 4.0 | 100% | Moderate |
| 6 PM | 1.8 | 2.1 | 100% | Low |
| 7 PM | 0.8 | 0.9 | 100% | Low |
| 8 PM | 0.2 | 0.2 | 100% | Low |
| 9 PM | 0.0 | 0.0 | 0% | Low |
| 10 PM | 0.0 | 0.0 | 1% | Low |
| 11 PM | 0.0 | 0.0 | 0% | Low |
The days ahead
Each day’s highest hour against its clear-sky ceiling, as far ahead as the model runs. CAMS forecasts about five days, so the table ends where the forecast does. The ceiling barely moves over that span; the modeled figure bounces with cloud.
| Day | Peak UV | Clear sky | Cloud | Category |
|---|---|---|---|---|
| Wed, Jul 22 today | 5 | 9 | 40% | Moderate |
| Thu, Jul 23 | 9 | 9 | 34% | Very high |
| Fri, Jul 24 | 9 | 9 | 82% | Very high |
| Sat, Jul 25 | 9 | 9 | 64% | Very high |
Cloud is the daylight-hours average for the day. Forecast, so the further out a row sits the more it moves.
Where today sits in the year
Today’s clear-sky ceiling is 9. At this latitude the clear-sky peak runs about 9–10 in late June and about 2 in late December, so the ceiling follows the season while cloud decides how much of it reaches the ground. A same-date comparison needs a year of stored days; 1450 are stored so far.
How this is built
Modeled estimates for Zionsville (about 39.951° N, 86.262° W), not a sensor reading. There is no public UV monitor in town. The figures come from the CAMS global model (ECMWF's Copernicus atmosphere service) through Open-Meteo, on a roughly 40 km grid, so read them as the shape of the day rather than a precise number. Cloud cover beside each hour comes from the weather model rather than CAMS; the clear-sky comparison is computed within CAMS alone. The clear-sky line is what the UV would reach with no cloud; the gap between the two lines is the model’s cloud estimate, not an observation of the sky. Hours already past are the model’s latest estimate of them, not a record of measurements, and later runs revise them. The figure at the top is interpolated between the two stored hours either side of the clock, which runs slightly off at the sunrise and sunset shoulders where the curve bends. Values are stored to two decimals and shown whole, the way the EPA reports the index. On the year view, the dashed comparison line is a 15-day centred average of the earlier years, weighted by how many years each date carries, and is not a climate normal. The stored hours are refreshed hourly.
Weather data by Open-Meteo.com, used under CC BY 4.0, from the CAMS global model.
Also for Zionsville: sunrise and sunset times and soil temperature.