Last updated: August 1, 2025
Understanding the UV Index in O'Fallon, Missouri, is essential for protecting your skin and maintaining overall health. With peaks reaching an intense 11 during midday, awareness of UV levels can help you prevent painful sunburns and long-term skin damage. O'Fallon's humid subtropical climate (Cfa) means residents are often exposed to high levels of ultraviolet radiation, particularly in the summer months. By monitoring the UV Index, you can take proactive steps to enjoy the outdoors safely, ensuring your skin stays healthy while you soak up the sun!
The UV Index throughout the day follows a predictable rise and fall, peaking at 11 around 1:00 PM. Starting at a modest 1 at 7:00 AM, it gradually escalates, reaching 10 by 12:00 PM, signaling the need for sun protection. As the afternoon progresses, the index dips from 11 to 8 by 3:00 PM, then declines further to 2 by 6:00 PM, and finally settles back at 1 by 7:00 PM. This data underscores the importance of taking precautions during the hours of peak UV exposure, particularly between 11:00 AM and 3:00 PM, when levels are highest and pose the greatest risk to skin health.
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 | 9 | very high | 15 min |
14:00 | 9 | very high | 15 min |
15:00 | 7 | high | 25 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, the UV Index exhibits noticeable seasonal changes, with the highest risk months being April to August, when the index reaches extreme levels of 10 and 11. During these peak months, particularly in June and July, the burn time shortens significantly to just 10 minutes, necessitating extra caution. In contrast, the winter months (January, February, and December) see moderate UV levels with burn times of 30 minutes. It is advisable for both visitors and residents to take protective measures, such as wearing sunscreen and protective clothing, especially from March to September, when the potential for skin damage from UV exposure becomes particularly high.
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 |
O'Fallon | 3 | 5 | 6 | 9 | 10 | 11 | 11 | 10 | 9 | 6 | 5 | 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 |