Last updated: May 3, 2025
Understanding the UV Index is crucial for residents of Louisville, United States, as it provides valuable information about the strength of ultraviolet radiation from the sun. With the city’s Cfa climate characterized by hot summers and mild winters, being aware of UV levels helps prevent sunburn and promotes long-term skin health. During peak sun hours, particularly between 10 AM and 2 PM, the UV Index can soar, reaching levels of 11, which indicates an extreme risk for harm from unprotected sun exposure. By staying informed about these levels, you can take necessary precautions to protect yourself and your loved ones from the harmful effects of the sun.
The UV Index throughout the day showcases a dynamic range of sun exposure, peaking dramatically at 12:00 PM with a maximum index of 10. Early morning hours start gently, with a mere 1 at 07:00 AM gradually rising to a moderate 4 by 09:00 AM. As the sun climbs higher, the index escalates to 9 by 11:00 AM and hits its zenith of 11 at 1:00 PM, indicating a critical level of UV radiation. Following the peak, there’s a noticeable decline; by 15:00 PM, the index dips to 7, continuing to taper off to 3 by 5:00 PM, before settling back to 1 as the evening sets in. Be sure to protect your skin during those peak hours to enjoy the sunshine safely!
| 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 | 9 | very high | 15 min |
| 12:00 | 10 | very high | 15 min |
| 13:00 | 11 | extreme | 10 min |
| 14:00 | 10 | very high | 15 min |
| 15:00 | 7 | high | 25 min |
| 16:00 | 5 | moderate | 30 min |
| 17:00 | 3 | moderate | 30 min |
| 18:00 | 1 | low | 45 min |
| 19:00 | 1 | low | 45 min |
Throughout the year, the UV Index reflects significant seasonal changes that affect sun exposure safety for both visitors and residents. From January to February, the UV levels remain moderate (3 to 5), allowing for a burn time of up to 30 minutes. A marked increase occurs in March, where the index rises to 7 (high exposure), reducing burn time to 25 minutes. The most critical months for UV exposure are April and May, with indices of 9 and 11, categorized as very high and extreme, where burn times drop to just 15 and 10 minutes respectively. June maintains this extreme risk, followed closely by a slight decrease in July (index of 10) and a resurgence in August and September (both at 9). October marks a return to high exposure (6), with burn times returning to 25 minutes, before descending back to moderate levels in November and December. Visitors and residents should be especially vigilant during April through September, utilizing appropriate sun protection measures, such as sunscreen, hats, and seeking shade, to minimize the risk of UV-related health issues.
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 | 7 | 9 | 11 | 11 | 10 | 9 | 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 |