Last updated: June 2, 2025
Understanding the UV Index is crucial for residents of Ontario, United States, as it plays a vital role in safeguarding your skin health. High UV levels can lead to sunburn, skin damage, and increase the risk of skin cancer, making awareness essential. With Ontario’s climate characterized by warm summers, it’s important to recognize the typical risks associated with UV exposure. During peak hours, the UV Index can reach levels as high as 10, indicating a very high risk of harm from unprotected sun exposure. Stay informed, and take the necessary precautions to enjoy the outdoors while protecting your skin!
From 07:00 to 08:00, the UV Index starts off mild with a maximum of 1 to 2, making it a safe time for early outdoor activities. As the sun climbs higher, the UV levels rise sharply, reaching 4 by 09:00 and hitting 6 by 10:00. The intensity peaks at 13:00 with a significant 10, indicating high exposure risk, perfect for applying sunscreen and seeking shade. As we move into the afternoon, levels gradually decrease, tapering to 9 by 14:00 and falling back to a more manageable 4 by 17:00. By evening, UV levels drop to 2 at 18:00 and retreat to 1 by 19:00, marking a safe return for those looking to enjoy twilight outdoors. Remember, it's essential to stay vigilant during those peak hours!
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 2 | low | 45 min |
| 09:00 | 4 | moderate | 30 min |
| 10:00 | 6 | high | 25 min |
| 11:00 | 8 | very high | 15 min |
| 12:00 | 9 | very high | 15 min |
| 13:00 | 10 | very high | 15 min |
| 14:00 | 9 | very high | 15 min |
| 15:00 | 8 | 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 UV Index fluctuates throughout the year, residents and visitors should be mindful of the changing sun exposure levels. During the winter months of January and December, the UV Index remains low at 2, allowing for longer safe exposure times of up to 45 minutes. However, as spring approaches, notable increases occur: March sees a rise to 6 (high exposure), while April and May escalate to 8 and 10 respectively, classified as very high, with burn times dropping to just 15 minutes. The peak UV risks are in May and June when the index reaches its highest at 10, making those months particularly hazardous for skin health. July and August maintain high levels, with UV indexes of 9, so protective measures are crucial. As summer gives way to autumn, the UV Index declines to 7 in September (high) and 5 in October (moderate), increasing the burn time. Finally, November drops back to a moderate level of 3. It is advisable for everyone to utilize appropriate sun protection during the high-risk months of April through September, particularly during peak hours, to mitigate the risk of skin damage.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Ontario | 2 | 4 | 6 | 8 | 10 | 10 | 9 | 9 | 7 | 5 | 3 | 2 |
| 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 |
| Houston UVI | 5 | 8 | 9 | 11 | 11 | 12 | 12 | 11 | 10 | 9 | 7 | 5 |