Louisville, KY UV Index Today
What is the UV index in Louisville right now?
0.9 Low
EPA describes low UV as needing no protection for most people.
Today's peak is 7.1 (High) at about 1pm local time.
When is UV strongest in Louisville today?
UV in Louisville peaks at 7.1 (High) around 1pm local time (GMT-4). It stays at 6 or above — the high band — for 4 hours, roughly 12pm to 4pm. UV is 3 or above for 6 hours.
Louisville today, in numbers
- Latitude
- 38.3°N — 71 of 121 from the north
- Today's peak
- 7.1 (High) — 56 of 121 nationally
- Peak arrives
- 1pm local (GMT-4)
- At or above 6
- 4 hours, 12pm to 4pm
- At or above 3
- 6 hours, 11am to 5pm
The window from 12pm to 4pm is the practical answer for Louisville 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 →
A heat island the index cannot see
Louisville has spent years being studied for its heat. Work by Georgia Tech’s Urban Climate Lab identified its urban heat island as one of the fastest-growing in the country, and the city commissioned an urban heat management study on the strength of that finding. All of it describes a surface effect: asphalt, brick and roofing take up the day’s radiation and hand it back as heat, and none of it changes the ultraviolet arriving from overhead. The hottest block in the metro and the most exposed block are not the same block, and the index does not distinguish them in either direction.
What does vary at street level is shade, and it varies more across this city than the sun does. Frederick Law Olmsted’s park system, laid out from the 1890s, leaves Cherokee, Iroquois and Shawnee Parks under mature cover, while TreesLouisville, the local canopy organization, works in neighborhoods it describes as having low canopy coverage and high heat. Those two conditions sit a few miles apart.
Heat and ultraviolet also run on different clocks through the day. The index peaks when the sun is highest and falls away with it. Air temperature peaks hours later, and in a heat island the stored warmth holds into the evening, long after the ultraviolet has gone. Judging one by the other gets the timing wrong by most of an afternoon.
Nearest metros we model
What does Louisville’s UV index mean today?
0.9 is Low. EPA describes low UV as needing no protection for most people. Today Louisville also reaches 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.
Modelled, not measured
The UV figures for Louisville 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 Louisville
What is the UV index in Louisville today?
When is UV strongest in Louisville today?
Is this measured or modelled?
Related
Updated