Last updated: July 2, 2025
In Alton, United States, staying informed about the UV Index is crucial for protecting your skin and promoting long-term health. Understanding UV levels helps you to prevent sunburn and reduce the risk of skin damage associated with high exposure to ultraviolet radiation. With Alton's humid continental climate (Dfa), summers can bring intense sunshine with UV Index levels soaring as high as 10 around midday. Being aware of these fluctuations enables you to enjoy the outdoors safely while safeguarding your skin against harsh UV rays.
The UV index begins its ascent at 07:00, starting at a gentle 1, then climbs gradually through the morning. By 10:00, it reaches a moderate 5, but from 11:00 onwards, the sun's intensity becomes pronounced, peaking at an impressive 10 between 13:00 and 14:00. After this zenith, the index dips to 8 at 15:00 and continues its decline, settling back to 2 by 18:00. As the day winds down into the evening, the UV index drops to a low 1 by 19:00, signaling a return to safer sun exposure levels. Enjoy the sunshine while staying protected during the high points!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 2 | 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 | 8 | 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 |
The UV Index exhibits significant seasonal fluctuations, with high-risk months generally occurring from April through September. During these months, the UV Index peaks, reaching an extreme level of 11 in June, where exposure should be limited to just 10 minutes to avoid sunburn. The remainder of the summer, particularly in July and August, also presents very high levels, suggesting burn times of only 15 minutes. Conversely, the winter months, particularly January and December, feature lower indices of 2 and 3, respectively, meaning sun exposure is less hazardous, allowing for burns in approximately 45 minutes. Residents and visitors are strongly advised to take necessary precautions during higher UV Index months, including wearing sunscreen, protective clothing, and seeking shade, especially between 11 a.m. and 3 p.m., when the sun is at its most intense. As the seasons change, adjusting sun safety practices is essential for safeguarding skin health.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Alton | 2 | 5 | 5 | 8 | 9 | 11 | 10 | 9 | 8 | 5 | 3 | 3 |
| 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 |