Last updated: May 3, 2025
Understanding the UV Index is essential for residents and visitors in Boston, as it serves as a vital indicator of solar radiation exposure and its potential effects on skin health. With Boston's temperate climate, where sunny days can lead to significant UV exposure, being aware of UV levels can help prevent sunburn and reduce the risk of long-term skin damage. From the peak index of 10 around noon to more moderate levels in the morning and evening, knowing when to seek shade or apply sunscreen is crucial for maintaining healthy skin while enjoying all that this vibrant city has to offer.
The UV Index throughout the day showcases a dynamic pattern of sun exposure, peaking during the afternoon. At 07:00, the index starts low at 1, gradually increasing as the sun rises. By 10:00, it reaches 6, signaling a rise in sun intensity, culminating in a striking 10 from 12:00 to 13:00, indicating a high risk of harm from unprotected sun exposure. As the day progresses, the UV Index declines, dropping to 3 by 17:00, and steadily returning to 1 by 19:00. This data highlights the importance of sun protection, especially during midday when the UV Index is at its highest.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 2 | low | 45 min |
| 09:00 | 4 | moderate | 30 min |
| 10:00 | 6 | high | 25 min |
| 11:00 | 8 | very high | 15 min |
| 12:00 | 10 | very high | 15 min |
| 13:00 | 10 | very high | 15 min |
| 14:00 | 9 | very high | 15 min |
| 15:00 | 8 | very high | 15 min |
| 16:00 | 5 | moderate | 30 min |
| 17:00 | 3 | moderate | 30 min |
| 18:00 | 2 | low | 45 min |
| 19:00 | 1 | low | 45 min |
Throughout the year, the UV Index experiences significant fluctuations, indicating varying levels of sun exposure risk. January and December see the lowest levels, with a moderate UV Index of 3, allowing for a burn time of 30 minutes. As spring approaches, March escalates to a high index of 7, reducing burn time to 25 minutes, while April and May peak at 9 and 10 respectively, categorizing them as very high risk months with burn times as low as 15 minutes. The intensity peaks in July at an extreme UV Index of 11, where just 10 minutes of exposure can lead to skin damage. Following summer, the risk remains high through August and September, before tapering into moderate levels in November. Residents and visitors should prioritize sun safety during March to October, taking precautions such as wearing sunscreen, protective clothing, and seeking shade during peak hours, especially in the summer months when the UV Index is at its highest.
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 |
| Boston | 3 | 5 | 7 | 9 | 10 | 10 | 11 | 10 | 8 | 7 | 5 | 3 |
| Los Angeles UVI | 4 | 6 | 8 | 9 | 10 | 11 | 11 | 10 | 10 | 7 | 5 | 4 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |