The UV index by city reference shows average peak daily UV index by month for major US cities. Use this to understand your UV exposure risk throughout the year and plan sun protection accordingly.
Average Monthly UV Index by City
| City | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
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How to Use the UV Index Reference
The UV index by city table shows monthly averages from EPA and NOAA data. Individual days vary based on cloud cover, time of year, and atmospheric conditions — check daily UV forecasts at weather.gov or weather apps for current readings.
Sun Protection Guidelines
For UV index 3+, wear SPF 30+ sunscreen, seek shade during peak hours (10am-4pm), and wear a hat and UV-blocking sunglasses. For UV index 8+, wear protective clothing including a UV-rated shirt (UPF 50+) and minimize time in direct sun between 10am and 4pm. Reapply sunscreen every 2 hours or after swimming or sweating.
For a detailed walkthrough, see our guide: UV Protection Guide.
FAQ
Is this UV index reference free?
Yes, completely free with no signup. Browse UV index data for major US cities by month.
What is a dangerous UV index?
UV index 3-5 (Moderate): wear sunscreen SPF 30+. UV 6-7 (High): reduce midday sun exposure. UV 8-10 (Very High): avoid sun 10am-4pm, wear protective clothing. UV 11+ (Extreme): take all precautions; unprotected skin can burn in minutes.
Which US cities have the highest UV index?
Cities at lower latitudes and higher altitudes have the highest UV. Honolulu, Miami, Phoenix, and Las Vegas regularly see summer UV indices of 11+. Cities in the Mountain West (Denver, Salt Lake City) also have high UV despite cooler temperatures due to elevation — UV increases ~10-12% per 1000 meters of altitude.
How does UV index change throughout the day?
UV index peaks around solar noon (typically 11am-2pm standard time, 12pm-3pm during daylight saving). Peak UV can be 80-90% of the daily maximum between 10am-4pm. UV is negligible before 8am and after 6pm. The UV index shown in weather apps is the peak daily forecast.
Do clouds protect from UV?
Not reliably. Light clouds reduce UV by only 10-25%. Heavy overcast can reduce UV 50-75%. UV reflects off water, sand, and snow — a beach or ski slope can expose you to more UV than the forecast suggests. Shadows from buildings and trees provide meaningful UV reduction.