Last updated: May 3, 2025
Understanding the UV Index in Portsmouth, United States, is essential for maintaining skin health and preventing sunburn, especially during the summer months when UV levels can soar. With a humid subtropical climate (Cfa), Portsmouth experiences heightened UV exposure that can lead to skin damage and increase the risk of skin cancer if precautions aren’t taken. By being aware of the daily UV Index, residents can make informed decisions about outdoor activities, ensuring they enjoy the sunshine safely and effectively protect their skin from harmful UV rays. Remember, the highest UV levels typically occur between 11 AM and 2 PM, peaking at a level of 10—a reminder to take action against overexposure during those critical hours!
The UV Index chart reveals a dynamic daily pattern of solar intensity. Starting early in the day, the UV Index remains low, peaking at 1 by 08:00. However, as the sun reaches its zenith, the index surges dramatically—hitting 7 by 11:00 and soaring to a maximum of 10 between 13:00 and 14:00. This signals a critical window for sun exposure, where protection is essential. As the afternoon progresses, the UV levels begin to decline, dropping to 4 by 17:00, before tapering off to 1 again by evening. To stay safe, it's vital to be cautious during those peak hours!
| 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 | 9 | very high | 15 min |
| 13:00 | 10 | very high | 15 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 |
Throughout the year, the UV Index exhibits significant seasonal fluctuations, with the highest levels occurring during the summer months. From March to September, the UV index reaches high to very high levels, peaking in May, June, and July at an index of 10, indicating a burn time of just 15 minutes. April also sees very high exposure with an index of 9. The months of March and October feature higher indexes of 7 and 6 respectively, classified as high, while the winter months of January, February, November, and December are categorized as moderate with indexes ranging from 3 to 5, allowing for longer exposure times of 30 minutes. Therefore, residents and visitors are advised to exercise extra caution during the high-risk months of April to September by using sunscreen, wearing protective clothing, and seeking shade, particularly during peak sun hours, to minimize the risk of 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 |
| Portsmouth | 3 | 5 | 7 | 9 | 10 | 10 | 10 | 9 | 8 | 6 | 5 | 3 |
| 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 |