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Madison, WI UV Index Today

Modelled for · GMT-5

What is the UV index in Madison right now?

0.4 Low

EPA describes low UV as needing no protection for most people.

Today's peak is 4.5 (Moderate) at about 11am local time.

When is UV strongest in Madison today?

UV in Madison peaks at 4.5 (Moderate) around 11am local time (GMT-5). It does not reach the high band at any hour today. UV is 3 or above for 5 hours.

Local time, midnight to midnight. Bar colour is the EPA UV band, never restyled.

Madison today, in numbers

Latitude
43.1°N — 22 of 121 from the north
Today's peak
4.5 (Moderate) — 107 of 121 nationally
Peak arrives
11am local (GMT-5)
At or above 6
not today
At or above 3
5 hours, 10am to 3pm

Madison never reaches the high band today; the midday hours still warrant a hat. 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 →

Frozen Lakes, Low Winter Sun, Reflected Beam

Downtown Madison sits on the isthmus between Lake Mendota and Lake Monona, around 850 feet above sea level. That is lake-level ground by any western standard, and a quarter of a kilometer of extra height does nothing measurable to the beam. Sun angle, cloud and the surface underfoot are the whole story here.

The solstices fix the range. At 43.07°N the noon sun stands about 70 degrees above the horizon in late June and tops out near 23 in late December. Winter cloud then works on the low end rather than the high one. January is Madison’s least-sunny month, at roughly 37 percent of possible sunshine, so the shortest sun and the thickest sky arrive together and the index stays down through that stretch almost regardless of what else happens.

The surface is where Madison stops behaving like an ordinary inland city. The World Health Organization puts fresh snow at up to 80 percent of incident ultraviolet reflected back upward, against under 10 percent for grass or soil. Both lakes freeze most winters and hold snow across their surface, so on a clear February or March afternoon out on the ice, part of the exposure arrives from underneath — off a surface the published index has no way to count.

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.

Milwaukee, WI 75 mi · 43.0°N peak 5.5 Chicago, IL 122 mi · 41.9°N peak 6 St. Paul, MN 224 mi · 44.9°N peak 2.7

What does Madison’s UV index mean today?

0.4 is Low. EPA describes low UV as needing no protection for most people. Today Madison also reaches Moderate 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 Madison 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 Madison

What is the UV index in Madison today?

0.4 right now (Low), peaking at 4.5 around 11am local time. It does not reach the high band today. This is a modelled value, not a ground measurement.

When is UV strongest in Madison today?

Around 11am local time (GMT-5), 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.

Madison air qualityThe AQI, from a regulatory monitor rather than a model UV across the USWhere Madison sits against every metro we track

Updated