Last updated: May 3, 2025
Understanding the UV Index is crucial for residents of Ontario, United States, as it plays a vital role in sunburn prevention and maintaining overall skin health. The UV Index provides a clear gauge of sun exposure levels, helping you make informed decisions about outdoor activities—especially during peak hours when the risk is highest. Ontario’s Dfb climate brings about varying seasons, but with summer months seeing noticeably elevated UV levels, it's essential to stay protected. Familiarize yourself with the daily UV Index trends, particularly the notable peaks around noon, to safeguard your skin against harmful rays and enjoy your time outside safely.
During the day, the UV Index fluctuates, providing a clear picture of sunlight intensity. Morning hours see a gentle rise, with values peaking at 1 from 7:00 AM to 8:00 AM, making it a safe time for outdoor activities. However, as the sun climbs higher, the index sharply escalates, hitting 3 by 9:00 AM and jumping to an intense 7 by 11:00 AM. The hottest moment arrives at 1:00 PM and 2:00 PM, where it reaches a peak of 10, indicating a high risk of harm from unprotected sun exposure. The intensity begins to wane in the afternoon, dipping to 6 at 4:00 PM and gradually descending to 1 by 7:00 PM, suggesting that early morning and late evening are the most favorable times to bask in the sun safely.
| 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 | 6 | high | 25 min |
| 17:00 | 4 | moderate | 30 min |
| 18:00 | 2 | low | 45 min |
| 19:00 | 1 | low | 45 min |
Throughout the year, UV exposure varies significantly, peaking in the late spring and summer months. April to August represent the high-risk period, with UV Index values reaching 10; indicating a very high exposure category and a burn time as short as 15 minutes. Visitors and residents should exercise caution and take protective measures, such as wearing sunscreen and protective clothing during these months. In contrast, January and December have moderate and low UV levels, respectively, with longer burn times of 30 to 45 minutes. Action is still advisable during these months, but the intensity is notably lower, allowing for safer outdoor activities. Overall, awareness of seasonal UV changes is essential for protecting skin health year-round.
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 |
| Ontario | 3 | 5 | 6 | 8 | 10 | 10 | 10 | 9 | 8 | 6 | 4 | 2 |
| 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 |