Last updated: May 3, 2025
In the Central Valley of the United States, awareness of the UV Index is crucial for safeguarding your skin health and preventing sunburn. With the region's distinctive Dfb climate, which features hot summers and moderate winters, the UV levels can rise sharply during the day, peaking at a dangerous 11 around midday. Understanding these fluctuations helps you make informed choices to protect yourself and your loved ones from the harmful effects of ultraviolet radiation, so you can enjoy the beautiful California sun without compromising your skin’s health. Stay vigilant and check the UV Index daily—your skin will thank you!
At sunrise, the UV Index begins its ascent, peaking at 1 by 07:00. As the day progresses, it rises steadily, hitting 2 by 08:00 and reaching a moderate 3 by 09:00. The intensity ramps up significantly from 10:00, where it soars to 6, and then it continues its climb to a striking 10 at 12:00. The highest point arrives at 13:00 and 14:00, where the UV Index maxes out at 11, signaling a time when sun protection is crucial. As the afternoon wanes, the index gradually decreases, settling at 9 by 15:00. By late afternoon, the values dip to 4 at 17:00, and then cool down to 2 by 18:00, before fading to 1 by 19:00 as daylight fades. It's a clear reminder to stay protected during the sunniest hours!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 2 | low | 45 min |
| 09:00 | 3 | moderate | 30 min |
| 10:00 | 6 | high | 25 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 experiences notable seasonal changes throughout the year, reaching its peak during the summer months. April through August are considered high-risk months for UV exposure, with indices consistently at 11-12, categorizing them as extreme. In these months, the burn time is reduced significantly to just 10 minutes, underscoring the need for protective measures. As the year transitions into fall, the UV Index begins to decline, with October and November still maintaining a high rating of 6-7. To ensure safety, both residents and visitors should be vigilant during the high-risk months by seeking shade, wearing protective clothing, and applying broad-spectrum sunscreen regularly. In contrast, during January and December, when the UV Index drops to 4, the risk is lower, allowing for more leisurely outdoor activities without as much concern for sunburn.
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 |
| Central Valley | 4 | 7 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 7 | 6 | 4 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |