Last updated: July 2, 2025
Understanding the UV Index is crucial for residents of Old Greenwich, United States, where sunny days invite outdoor activities but also elevate the risk of harmful UV exposure. With a climate classified as Cfa, the area experiences high levels of UV radiation, particularly during midday when the index peaks at 9 (between 12:00 and 14:00). Being aware of UV levels isn’t just about avoiding sunburn; it plays a pivotal role in maintaining overall skin health and preventing long-term damage. By staying informed and taking appropriate precautions, you can enjoy the beautiful outdoor scenery of Old Greenwich while protecting your skin from UV risks.
The UV Index throughout the day presents a clear pattern of intensity, peaking at midday. Starting from a mild level of 1 at 07:00, the index rises steadily, reaching 2 by 08:00. The real surge occurs between 09:00 and 13:00, where it escalates from 4 to a striking 9—the highest point of the day. As the afternoon unfolds, the intensity slightly declines to 7 at 15:00, before tapering off to 5 at 16:00. The evening sees a further decrease, settling back to 2 by 18:00 and returning to 1 at 19:00. For those enjoying outdoor activities, it’s essential to take precautions, especially during the peak hours from 11:00 to 14:00 when the UV rays are most potent.
| 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 | 9 | very high | 15 min |
| 13:00 | 9 | very high | 15 min |
| 14:00 | 9 | very high | 15 min |
| 15:00 | 7 | high | 25 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 notable fluctuations, with high-risk months typically spanning from March to September. In April and May, the Index peaks at 10, indicating a very high exposure category where the burn time is just 15 minutes. Consequently, during these months, it is crucial for both visitors and residents to take precautions such as wearing sunscreen, protective clothing, and sunglasses. The risk slightly diminishes in October with a UV Index of 6, shifting to lower levels by November and December, where the Index falls to 4 and 2, respectively. As the year progresses, individuals are encouraged to adjust their sun safety practices according to these seasonal changes to ensure their skin health remains a priority.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Old Greenwich | 3 | 5 | 6 | 8 | 10 | 10 | 9 | 9 | 8 | 6 | 4 | 2 |
| 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 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |