Last updated: May 3, 2025
In Thornton, United States, being aware of the UV Index is crucial for protecting your skin and maintaining long-term health. Understanding the daily fluctuations in UV levels helps residents and visitors alike prevent sunburn and reduce the risk of skin cancer, especially during peak hours when the index reaches a high of 11 between noon and 2 PM. With a Cfa climate characterized by warm summers, the sun’s intense rays can pose significant risks, making it essential to stay informed about UV exposure. By keeping an eye on the UV Index, you can enjoy the beautiful Colorado sunshine while safeguarding your skin's health.
The UV Index for the day showcases a striking pattern, starting moderate at 7:00 AM with a value of 1. As the sun climbs higher, the index steadily rises, hitting 3 by 9:00 AM, and then surging to a peak of 11 between 1:00 PM and 2:00 PM. This indicates a high risk of harm from unprotected sun exposure during midday. Following the peak, the UV Index gradually declines to 4 by 5:00 PM and further decreases to 1 by 7:00 PM, emphasizing the critical importance of sun protection during the intense midday hours. It’s advisable to seek shade and wear sunscreen if you're outside during the peak period!
| 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 | 8 | very high | 15 min |
| 12:00 | 10 | very high | 15 min |
| 13:00 | 11 | extreme | 10 min |
| 14:00 | 11 | extreme | 10 min |
| 15:00 | 9 | very high | 15 min |
| 16:00 | 7 | high | 25 min |
| 17:00 | 4 | moderate | 30 min |
| 18:00 | 2 | low | 45 min |
| 19:00 | 1 | low | 45 min |
The UV Index varies significantly throughout the year, indicating changes in sun exposure risk. Notably, March through September presents the highest risk, peaking in July with an intense UV Index of 12, categorized as extreme, and a burn time of just 10 minutes. April, May, June, and August maintain similarly high levels, all falling under the extreme category. The high-risk months where caution is particularly warranted are February through October, with March to August being critical for sun safety. Residents and visitors should take precautions during these months, such as wearing protective clothing, using broad-spectrum sunscreen, and seeking shade, particularly during peak hours of sunlight, to minimize the risk of skin damage. As the seasons transition, January and December demonstrate lower levels (UV Index 4), with moderate exposure risk, allowing for more lenient outdoor activities.
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 |
| Los Angeles UVI | 4 | 6 | 8 | 9 | 10 | 11 | 11 | 10 | 10 | 7 | 5 | 4 |
| Thornton | 4 | 7 | 8 | 11 | 11 | 11 | 12 | 11 | 10 | 8 | 6 | 4 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |