Last updated: July 2, 2025
Understanding the UV Index is crucial for residents of Louisville, as it provides essential information about the sun’s harmful ultraviolet rays. With a climate characterized by hot summers and a USDA climate zone of Dfa, Louisville's exposure to UV radiation can put individuals at risk for sunburn and long-term skin health issues. By being aware of the UV levels throughout the day—especially during peak hours like 12 PM to 2 PM, when the index climbs to 10—you can take proactive measures to protect your skin while enjoying outdoor activities. Don’t underestimate the power of the sun; staying informed about UV exposure is key to maintaining your skin’s health and safety.
During the day, the UV Index fluctuates, providing a clear picture of sunlight intensity. Morning hours see a gentle rise, with values peaking at 1 from 7:00 AM to 8:00 AM, making it a safe time for outdoor activities. However, as the sun climbs higher, the index sharply escalates, hitting 3 by 9:00 AM and jumping to an intense 7 by 11:00 AM. The hottest moment arrives at 1:00 PM and 2:00 PM, where it reaches a peak of 10, indicating a high risk of harm from unprotected sun exposure. The intensity begins to wane in the afternoon, dipping to 6 at 4:00 PM and gradually descending to 1 by 7:00 PM, suggesting that early morning and late evening are the most favorable times to bask in the sun safely.
| 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 | 10 | very high | 15 min |
| 14:00 | 10 | very high | 15 min |
| 15:00 | 9 | very high | 15 min |
| 16:00 | 6 | 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 varies significantly, peaking during late spring and summer months. High-risk months for UV exposure are April through September, where the UV Index frequently reaches levels classified as very high; particularly notable are May, June, and July, when it consistently hits a maximum of 10. Visitors and residents are advised to take precautions during these months, with burn times dramatically reduced to as little as 15 minutes. In contrast, January, February, and November present moderate UV levels, and December has a low index, making sun safety measures less critical during these months. To protect against skin damage, it is essential to wear sunscreen, seek shade, and wear protective clothing, especially between peak months of April and September.
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 |
| Louisville | 3 | 5 | 6 | 9 | 10 | 10 | 10 | 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 |