Last updated: June 2, 2025
Understanding the UV Index is essential for residents and visitors in Cook, United States, where the climate can lead to varied UV exposure risks throughout the day. With maximum UV levels peaking at 9 during midday, it’s crucial to be aware of these fluctuations to prevent sunburn and protect your skin health. Recognizing the dangers of excessive sun exposure is key, especially in a Dfb climate where clear skies can intensify UV radiation. By staying informed, you can enjoy outdoor activities while taking the necessary precautions to keep your skin safe and healthy.
The UV Index throughout the day showed a pronounced peak around midday, starting with a maximum reading of 1 at 7:00 AM. As the sun rose, the index climbed steadily, reaching 9 between 12:00 PM and 2:00 PM—the highest levels of the day, indicating a strong need for sun protection. The intensity began to taper off after 3:00 PM, with readings of 8 at 3:00 PM, dropping to 6 by 4:00 PM, and further decreasing to 1 by 7:00 PM. Overall, the UVI highlights the importance of sun safety during the peak hours, especially between 11:00 AM and 2:00 PM.
| 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 | 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 | 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 |
Throughout the year, the UV Index experiences significant seasonal changes, impacting sun exposure and burn times. January and December see low UV levels (Index 2), with burn times of 45 minutes, while February and November moderate (Index 3), reducing burn time to 30 minutes. As spring arrives, March (Index 5) indicates a moderate risk before transitioning to April's high level (Index 7) with a burn time of 25 minutes. The peak risk occurs in May and June, where the UV Index reaches 8 to 9, categorizing exposure as very high and necessitating protective measures within just 15 minutes of sun exposure. July continues this trend, while August sees a slight decrease to 8. The UV Index tapers off in September (Index 7), October (Index 5), and November (Index 3), before returning to low levels in December. Visitors and residents are advised to take extra precautions during May through August, including wearing protective clothing, applying sunscreen, and seeking shade during peak hours to minimize the risk of UV exposure.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cook | 2 | 3 | 5 | 7 | 8 | 9 | 9 | 8 | 7 | 5 | 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 |