Last updated: July 2, 2025
Understanding the UV Index is crucial for residents of Joanna, United States, where the climate often exposes individuals to varying levels of ultraviolet radiation throughout the day. As the sun reaches its peak intensity, particularly around midday, the UV index can escalate to dangerous levels—reaching highs of 11 during the summer months. This makes it especially important to be aware of UV levels to prevent sunburn and protect skin health from long-term damage. With Joanna’s humid subtropical climate (Cfa), outdoor activities are a part of daily life, so staying informed about UV exposure risks is essential for everyone enjoying the sun.
During the day, the UV Index exhibits a striking pattern as it peaks in the late morning and early afternoon. Starting from a modest value of 1 at 07:00, the index gradually climbs, reaching 3 by 09:00. Expect a sharp increase around 10:00, when it soars to 5, and it doesn't stop there; by noon, it hits an impressive 10. The highest point of the day occurs at 13:00, with a peak of 11, indicating a critical time for sun exposure. As the afternoon progresses, the index begins to decline, falling to 10 at 14:00 and tapering off to 9 at 15:00. By evening, the UV Index diminishes steadily, finishing the day back at 1 by 19:00. This data emphasizes the importance of protective measures during the high noon hours when UV levels are at their most intense.
| 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 | 10 | very high | 15 min |
| 13:00 | 11 | extreme | 10 min |
| 14:00 | 10 | very high | 15 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 |
As the seasons change, the UV Index demonstrates considerable variation, impacting burn potential and risk levels for skin exposure. The highest risk months occur from March to August, with values peaking at 11 during May, June, and July, indicating an extreme exposure category with a burn time of just 10 minutes. February marks a shift into a high risk category, while September through November gradually decreases the UV levels, transitioning back to moderate by December. It is crucial for visitors and residents alike to exercise caution during these high-risk months by wearing protective clothing, applying sunscreen regularly, and seeking shade to mitigate the potential for skin damage.
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 |
| Joanna | 4 | 7 | 8 | 10 | 11 | 11 | 11 | 10 | 9 | 8 | 6 | 4 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |