# Riverside, CA UV Index Today — hourly UV forecast > Source: https://breathecheck.com/uv-index/us/california/riverside/ > UV index in Riverside, CA right now, today's peak and the hour it arrives, on the EPA scale. Modelled data, labelled as modelled. # Riverside, CA UV Index Today Modelled for 14 Sep 2026, 22:00 UTC · GMT-7 ## What is the UV index in Riverside right now? 5.7 High EPA suggests shade between 10am and 4pm, plus a shirt and sunscreen. Today's peak is 9.4 ( Very High ) at about 1pm local time. ## When is UV strongest in Riverside today? UV in Riverside peaks at 9.4 (Very High) around 1pm local time (GMT-7). It stays at 6 or above — the high band — for 4 hours, roughly 11am to 3pm. UV is 3 or above for 7 hours. Local time, midnight to midnight. Bar colour is the EPA UV band, never restyled. ## Riverside today, in numbers - **Latitude**: 34.0°N — 94 of 121 from the north - **Today's peak**: 9.4 (Very High) — 4 of 121 nationally - **Peak arrives**: 1pm local (GMT-7) - **At or above 6**: 4 hours, 11am to 3pm - **At or above 3**: 7 hours, 10am to 5pm The window from 11am to 3pm is the practical answer for Riverside today. Nationally today the spread runs 11.4 in Hilo (20°N) to 1.3 in Fargo (47°N). Why latitude and the clock decide this → ## The marine layer arrives here already spent Whatever cloud the Pacific sends inland has usually run out before it gets this far. Stratus forms over the cold water off Southern California and pushes ashore overnight, at its deepest in late spring, but close to fifty miles of warming inland air takes most of it apart on the way. Mornings that stay gray at the beach are frequently open sky in this valley, and on the days the deck does reach the Inland Empire it tends to arrive thin and leave early. A forecast written for the coastline is describing a different morning than the one Riverside gets. The rest of the year gives the sky almost nothing to do. Summer here passes month after month with no measurable rain, so for a long stretch the index answers to sun angle and very little else. Cloud stops being the daily variable it is across most of the country. The reading moves less from one day to the next than the same reading would east of the Rockies, and the seasonal curve is smoother than a single number on any given afternoon would suggest, which makes the shape of the year more informative here than the day-to-day. ## Nearest metros we model UV changes with latitude, not with a city boundary, so a neighbour a hundred miles north reads differently for a reason. ## What does Riverside’s UV index mean today? 5.7 is High. EPA suggests shade between 10am and 4pm, plus a shirt and sunscreen. Today Riverside also reaches Very High at its peak — a different band from the one it is in right now, which is why the hour matters as much as the day. The scale is open-ended: 11 is where the named bands stop, not the maximum. All five bands, with the EPA guidance for each → ## Modelled, not measured The UV figures for Riverside are computed by the Copernicus atmosphere model, not read off an instrument here — unlike the AQI on our air-quality pages, which comes from a regulatory monitor . Cloud is where a UV model is weakest. What that means in practice → ## Questions about UV in Riverside **What is the UV index in Riverside today?** 5.7 right now (High), peaking at 9.4 around 1pm local time. UV stays at 6 or above for 4 hours, from about 11am to 3pm. This is a modelled value, not a ground measurement. **When is UV strongest in Riverside today?** Around 1pm local time (GMT-7), not at noon — solar noon drifts across a timezone and daylight saving moves it later on the clock. **Is this measured or modelled?** Modelled. The figures come from the Copernicus atmosphere model via Open-Meteo , unlike the AQI on our air-quality pages, which is read from an EPA regulatory monitor. Cloud cover is where a UV model is weakest. ## Related On this page Air quality alerts We alert on AQI, not UV — UV is predictable from the calendar, air quality is not. Updated 14 Sep 2026, 22:00 UTC