UV Index in Boston, United States

Last updated: May 3, 2025

In Boston, understanding the UV Index is crucial for protecting yourself from harmful ultraviolet rays. With the city’s Cfa climate—characterized by hot summers and cold winters—sun exposure can lead to serious skin health issues if not managed properly. The UV levels can peak dramatically during midday, reaching a maximum of 10 around 1 PM, which significantly increases the risk of sunburn. By staying informed about the UV Index, you can make safer choices when heading outdoors, ensuring your skin remains healthy while you enjoy all that Boston has to offer.

Hourly UV Index in Boston

As the sun rises, the UV Index begins its ascent, peaking at an invigorating 10 by 1:00 PM. Early morning, from 7:00 AM to 8:00 AM, sees a mild 1 to 2, making it a perfect time for a leisurely stroll. By 9:00 AM, the UV Index reaches 3, signaling a need for some sun protection. The real intensity kicks in around 11:00 AM, hitting 8, and just after noon, it soars to its daily maximum of 9. The afternoon hours see a slight decline, with values tapering from 9 at 2:00 PM to 6 by 4:00 PM. As daylight wanes, the UV Index gently drops to 1 by 7:00 PM, wrapping up a day of vibrant sunlight but reminding us to stay vigilant during those peak hours. Remember to reapply sunscreen and seek shade to keep safe while enjoying those sunny moments!

Average solar exposure data for the current time of the year. Actual values may vary and depend on many factors, such as cloud cover, vegetation cover, surface type, etc.
TimeUVICategoryTime to Burn
07:001low45 min
08:002low45 min
09:003moderate30 min
10:006high25 min
11:008very high15 min
12:009very high15 min
13:0010very high15 min
14:009very high15 min
15:008very high15 min
16:006high25 min
17:004moderate30 min
18:002low45 min
19:001low45 min

Monthly UV Index Trends in Boston

Throughout the year, the UV Index experiences notable fluctuations, indicating varying levels of sun exposure risk. The high-risk months occur from March to September, peaking in May and June with a UV Index of 10, classified as very high. This signifies a decrease in safe sun exposure time to just 15 minutes. In contrast, the lower UV Index months are January (3) and December (2), categorized as moderate and low, with burn times of 30 and 45 minutes, respectively. Residents and visitors are advised to take protective measures such as wearing sunscreen, protective clothing, and seeking shade, especially during the summer months when UV levels are at their highest. It is essential to stay informed and adjust sun exposure accordingly to minimize the risk of skin damage.

Monthly Maximum UV Index for Boston, United States

The monthly maximum UV Index (UVI) represents the highest UV radiation level recorded each month in Boston. It measures the strength of ultraviolet radiation from the sun and helps assess the risk of sunburn and UV-related health issues.
JanFebMarAprMayJunJulAugSepOctNovDec357910101098642
Data source: Statistical UV Index data for Boston, based on information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

Compare Boston UV Index with Other United States Cities

The table above highlights how UV exposure in Boston compares to other major locations across United States. This comparison helps travelers and residents better understand regional sun intensity and plan outdoor activities with sun safety in mind.
Boston's solar exposure compared to other cities in United States. Generated using Copernicus Atmosphere Monitoring Service information.
 JanFebMarAprMayJunJulAugSepOctNovDec
Chicago UVI34689101098642
Brooklyn UVI35681010998642
New York City UVI35681010998642
Boston357910101098642
Los Angeles UVI46891011111010754
Houston UVI589111112121110975