Last updated: May 3, 2025
Understanding the UV Index is crucial for anyone visiting the Grand Canyon, where the stunning vistas come with significant sun exposure risks. In this remarkable desert climate, where temperatures soar and the sun shines brightly, awareness of UV levels can help prevent painful sunburns and long-term skin health issues. With midday UV Index levels reaching as high as 12, the potential for harmful effects is significant, making it essential to take precautions during outdoor activities. Whether you're hiking the trails or simply soaking in the breathtaking views, knowing how to manage your sun exposure is vital for a safe and enjoyable experience in this iconic landscape.
As the sun rises, the UV Index begins its ascent, starting at a mild 1 at 07:00. By 08:00, it increases to a moderate 3, but the real surge comes just before noon. The index peaks at an intense 12 during the midday hours, specifically at 12:00, urging sun protection for those outdoors. Following this high, a gradual decrease occurs, with the values declining to 10 by 14:00, then tapering off to 7 at 15:00. As the day wanes, the UV intensity drops significantly, falling to 1 by 19:00, signifying a much safer period for sun exposure. This hourly UVI cycle illustrates a clear pattern: the importance of seeking shade and wearing sunscreen during the peak hours when the sun’s rays are the strongest.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 3 | moderate | 30 min |
| 09:00 | 6 | high | 25 min |
| 10:00 | 8 | very high | 15 min |
| 11:00 | 11 | extreme | 10 min |
| 12:00 | 12 | extreme | 10 min |
| 13:00 | 11 | extreme | 10 min |
| 14:00 | 10 | very high | 15 min |
| 15:00 | 7 | high | 25 min |
| 16:00 | 4 | moderate | 30 min |
| 17:00 | 2 | low | 45 min |
| 18:00 | 1 | low | 45 min |
| 19:00 | 1 | low | 45 min |
Throughout the year, UV Index levels exhibit significant seasonal changes, with high-risk months predominantly from February to August. The UV Index peaks at 12 during the summer months of May, June, July, and August, categorizing exposure as extreme and resulting in a burn time of just 10 minutes. Visitors and residents are strongly advised to take protective measures during these times, such as wearing sunscreen, protective clothing, and seeking shade during peak hours. Conversely, January, November, and December present moderate UV levels (Index 4-5), where burn times extend to 30 minutes, indicating a lower risk of UV-related harm. As seasons transition, awareness and proactive sun safety become crucial in protecting skin health.
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 |
| Grand Canyon | 4 | 7 | 9 | 11 | 12 | 12 | 12 | 11 | 10 | 8 | 5 | 4 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |