Last updated: July 2, 2025
Understanding the UV Index is crucial for residents and visitors of Boston. As a city with a humid subtropical climate, Boston experiences varying UV levels throughout the year, making it vital to monitor these levels for effective sunburn prevention and overall skin health. During peak summer hours, the UV Index can reach a high of 11, indicating extreme risk of harm from unprotected sun exposure. Staying informed about the UV Index not only helps protect your skin but also enhances your outdoor experience in this vibrant city, where sunny days call for fun in the sun!
The hourly UV Index paints a vivid picture of the sun's intensity throughout the day. Starting off gently in the early morning, with maximum readings of 1 at 07:00 and 08:00, it gradually begins to climb. By 09:00, it reaches 3, signaling a noticeable increase in UV exposure. The sun peaks dramatically at 12:00, soaring to a 10, reaching its zenith with a maximum of 11 at both 13:00 and 14:00—a prime time for sun protection. As the afternoon slips into evening, the UV Index begins to recede, dropping to 8 by 16:00, and then tapering off to 5 at 17:00. The day winds down with a safe 3 at 18:00 and returns to a manageable 1 by 19:00, reminding us to stay vigilant and enjoy the sun responsibly throughout the day.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 1 | low | 45 min |
| 09:00 | 3 | moderate | 30 min |
| 10:00 | 5 | moderate | 30 min |
| 11:00 | 8 | very high | 15 min |
| 12:00 | 10 | very high | 15 min |
| 13:00 | 11 | extreme | 10 min |
| 14:00 | 11 | extreme | 10 min |
| 15:00 | 10 | very high | 15 min |
| 16:00 | 8 | very high | 15 min |
| 17:00 | 5 | moderate | 30 min |
| 18:00 | 3 | moderate | 30 min |
| 19:00 | 1 | low | 45 min |
Throughout the year, UV Index levels fluctuate significantly, with the highest risk observed during the spring and summer months. From February to August, the UV Index remains at a very high to extreme level, peaking at 11 in May, June, July, and August, where the burn time is as short as 10 minutes. Visitors and residents are advised to take extra precautions during these months by wearing protective clothing, applying sunscreen regularly, and seeking shade, especially during midday hours. In contrast, January and December experience moderate UV levels, allowing for longer exposure times of 30 minutes before burning. As the UV levels decline entering the fall months, particularly in November with a high index of 6 (burn time of 25 minutes), it is still prudent to remain vigilant against UV exposure.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Chicago UVI | 3 | 4 | 6 | 8 | 9 | 10 | 10 | 9 | 8 | 6 | 4 | 2 |
| Brooklyn UVI | 3 | 5 | 6 | 8 | 10 | 10 | 9 | 9 | 8 | 6 | 4 | 2 |
| New York City UVI | 3 | 5 | 6 | 8 | 10 | 10 | 9 | 9 | 8 | 6 | 4 | 2 |
| Los Angeles UVI | 4 | 6 | 8 | 9 | 10 | 11 | 11 | 10 | 10 | 7 | 5 | 4 |
| Boston | 5 | 8 | 9 | 10 | 11 | 11 | 11 | 11 | 10 | 8 | 6 | 4 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |