Last updated: June 2, 2025
Understanding the UV Index in St. Charles, United States is crucial for residents and visitors alike, as it provides essential insights into daily sun exposure and its potential health impacts. With the risk of sunburn and long-term skin damage heightened during peak UV levels, knowing when to seek shade or apply sunscreen can safeguard skin health. St. Charles, located in a humid continental climate (Dfa), often experiences significant UV exposure, especially during the summer months when midday levels can reach a maximum of 10. Stay informed to enjoy the beautiful outdoors while protecting your skin from harmful ultraviolet rays!
At dawn, the UV Index starts off gently at 1 by 7:00 AM, barely warranting sun protection. As the morning unfolds, it gradually climbs to 2 by 8:00 AM and reaches 4 at 9:00 AM, signaling moderate exposure risk. The sun peaks at noon with a maximum of 10, indicating high risk for harm from unprotected sun exposure. From 1:00 PM to 2:00 PM, the UV Index holds steady at 10, urging everyone to stay mindful of their sun safety. As the afternoon progresses, the levels decline, dipping to 9 at 2:00 PM and falling further to 5 by 4:00 PM. By evening, the index reduces to 1 by 7:00 PM, allowing for a safe outdoor experience as daylight dims. It’s clear that the midday hours require vigilance against sun exposure, while early and late hours provide a more relaxed approach.
| 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 | 10 | very high | 15 min |
| 14:00 | 9 | very high | 15 min |
| 15:00 | 8 | very high | 15 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, UV exposure varies significantly, with notable peaks between March and October. The high-risk months are April to August, where the UV Index consistently reaches very high levels of 8 to 10 and the burn time reduces to just 15 minutes. In contrast, the low-risk months of November and December see UV Index values fall to 3 and 2, respectively, allowing for safe exposure times of up to 30 and 45 minutes. Residents and visitors are advised to take extra precautions during the high-risk months by seeking shade, wearing protective clothing, and applying sunscreen regularly to mitigate the increased risk of sunburn and skin damage.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| St. Charles | 3 | 4 | 6 | 8 | 9 | 10 | 10 | 9 | 8 | 6 | 3 | 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 |