When Is UV Strongest? The 10 a.m.-4 p.m. Window and Solar Noon Explained
UV peaks around solar noon, not whenever it feels hottest - here's how to time your outdoor plans around the strongest hours.
UV peaks within an hour or two of solar noon (roughly 12-2 p.m. with daylight saving time), which is why agencies advise limiting sun exposure from 10 a.m. to 4 p.m.
The EPA advises limiting time in the sun during the midday hours of roughly 10 a.m. to 4 p.m., when UV rays are most intense because the sun is high in the sky near solar noon.
Questions we get a lot
What time of day is UV the strongest?
UV intensity peaks within an hour or two of solar noon, which is roughly 12-2 p.m. when daylight saving time is in effect. This is when the sun is highest in the sky, so UV rays travel the shortest path through the atmosphere.
Why do agencies say to avoid the sun from 10 a.m. to 4 p.m.?
Because UV exposure is highest around midday, the EPA advises limiting time in the sun during the 10 a.m. to 4 p.m. window. Scheduling outdoor activities outside those hours, or using shade and sunscreen during them, reduces UV exposure.
Is solar noon the same as the hottest part of the day?
Not exactly. Solar noon is when the sun is highest in the sky, which drives peak UV, but air temperature usually peaks a bit later in the afternoon. That's why you can get the most UV before it feels hottest - so use the UV Index, not the heat, to gauge risk.
r/running: 'I always run at 1 p.m. - is that the worst possible time for sun exposure?'