Last updated: May 3, 2025
Understanding the UV Index in Philadelphia is crucial for anyone looking to protect their skin from harmful ultraviolet radiation. With its humid subtropical climate, Philadelphia experiences varying UV levels throughout the day, peaking between 11 AM and 2 PM when the sun's intensity can reach a dangerous 11 on the UV scale. Being aware of these levels can help residents and visitors alike take essential precautions against sunburn, skin damage, and long-term health risks such as skin cancer. Whether you’re enjoying the beautiful parks or exploring urban attractions, staying informed about the UV Index ensures that your time in the sun is both enjoyable and safe.
As the sun rises on this vibrant day, the UV Index begins its steady ascent. Starting at a mild 1 at 07:00, it quickly climbs to 3 by 09:00, signaling that it’s time to enjoy some outdoor activities with caution. By 10:00, the index reaches a moderate 5, but the real heat kicks in at 11:00, peaking at an intense 11 from 13:00 to 14:00. During this peak, sun protection is crucial, especially for those planning to be outdoors. As the afternoon progresses, the UV Index gently declines, dropping to 7 by 16:00 and tapering off to 4 by 17:00. As the sun sets, the index returns to 1 by 19:00, marking a gentle end to a day of vibrant sunlight.
| 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 | 9 | very high | 15 min |
| 16:00 | 7 | high | 25 min |
| 17:00 | 4 | moderate | 30 min |
| 18:00 | 2 | low | 45 min |
| 19:00 | 1 | low | 45 min |
Throughout the year, UV exposure levels vary significantly, with high-risk months typically occurring from March to August when the UV Index reaches its peak at 11, categorized as extreme. March and April also feature very high levels, making these months crucial for sun safety awareness. Visitors and residents should be particularly cautious during this period, applying sunscreen regularly, wearing protective clothing, and seeking shade during peak hours. In contrast, the months of January, November, and December present a moderate UV Index of 3 to 5, allowing for more relaxed precautions, though it's still important to remain mindful of sun exposure. Always check local UV forecasts and adjust your sun safety practices accordingly to protect your skin 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 |
| Los Angeles UVI | 4 | 6 | 8 | 9 | 10 | 11 | 11 | 10 | 10 | 7 | 5 | 4 |
| Philadelphia | 3 | 6 | 8 | 10 | 11 | 11 | 11 | 10 | 9 | 7 | 5 | 3 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |