Last updated: July 2, 2025
Understanding the UV Index in Cambridge, Massachusetts is crucial for maintaining healthy skin and preventing sunburn, especially during the warmer months. The UV Index provides a daily forecast of the sun's strength, helping residents and visitors stay informed about exposure risks. In Cambridge's Dfa climate, characterized by hot summers, the UV levels can reach as high as 11 during peak hours—a reminder to take protective measures. By keeping an eye on the UV Index, you can enjoy the sun safely while minimizing the risks associated with overexposure, ensuring your skin remains healthy and protected all season long.
As the sun rises, the UV Index remains relatively low, starting at a gentle 1 from 07:00 to 09:00. However, as the day progresses, the UV levels ramp up significantly, reaching a moderate 5 by 10:00 and hitting a peak of 11 between 13:00 and 14:00. This period signifies the highest risk, urging outdoor enthusiasts to take precautions. By 15:00, the index starts to dip to 10, followed by a gradual decline to 5 at 17:00, and settling at 2 by 19:00. It's a clear reminder that during midday, when the sun is at its strongest, the need for protection is paramount to safeguard against harmful UV radiation. Enjoy the sunshine, but don't forget your sunscreen! ☀️
| 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 | 7 | high | 25 min |
| 12:00 | 9 | 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 | 2 | low | 45 min |
Throughout the year, UV exposure varies significantly, with high-risk months typically occurring from March to September. During these months, particularly in April through July, the UV index reaches notably high levels, peaking at 11, which indicates extreme exposure risks and a quick burn time of just 10 minutes. As the seasons shift, visitors and residents should be particularly vigilant from May to August, when protective measures such as sunscreen, hats, and seeking shade are essential to prevent skin damage. In contrast, January, November, and December present a moderate UV index of 3-4, allowing for longer burn times of 30 minutes, though sunscreen should still be applied. Staying informed about these UV changes can help ensure safe outdoor activities year-round.
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 |
| Cambridge | 3 | 5 | 7 | 9 | 10 | 11 | 11 | 10 | 9 | 6 | 4 | 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 |