Last updated: May 3, 2025
Understanding the UV Index in Johnston, United States is crucial for safeguarding your skin and overall health. Awareness of UV levels helps prevent painful sunburns and long-term skin damage, making it essential for residents and visitors alike. With Johnston's Cfa climate, characterized by warm summers and varying exposure risks, knowing when to take precautions can make all the difference. During peak hours, especially between 10 AM and 2 PM, the UV Index can reach highs of 11, emphasizing the importance of staying informed and protected from harmful ultraviolet radiation.
The UV Index reveals a dynamic sun intensity throughout the day, peaking dramatically in the midday hours. Starting off at a mild 1 at 07:00 and 08:00, the UV Index begins to climb sharply, reaching 3 by 09:00. As the sun ascends, it escalates to 5 at 10:00 and surges to 10 by noon, marking a significant rise in solar exposure. The highlight of the day occurs at 13:00 with a staggering 11, indicating severe UV levels. Following this zenith, the index gradually dips, dropping to 9 by 15:00 and continuing downward to 2 by 18:00. Finally, as the day winds down, the UV Index returns to a low 1 by 19:00. This data underscores the importance of sun safety, particularly during those peak hours when protection is essential.
| 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 | 6 | 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, so does the UV Index, which significantly impacts exposure levels throughout the year. January starts with a moderate UV Index of 4, allowing for a burn time of 30 minutes. However, February ramps up to a high index of 7, with a reduced burn time of 25 minutes. The peak months, from March through August, experience extreme UV levels, particularly in May and June, where the UV Index reaches 11 and burn times shrink to just 10 minutes. September and October see a slight decrease, yet still maintain a very high index of 9 and 8, respectively. The year concludes with lower levels in November and December. Visitors and residents should take special care during the high-risk months from March to August, ensuring proper sun protection measures, such as wearing sunscreen, hats, and protective clothing, to mitigate the risk of UV-related harm.
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 |
| Johnston | 4 | 7 | 8 | 10 | 11 | 11 | 11 | 11 | 9 | 8 | 6 | 4 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |