Last updated: May 3, 2025
In Thunder Bay, Canada, being aware of the UV Index is vital for protecting your skin and maintaining overall health. Understanding UV levels can significantly aid in sunburn prevention and reducing long-term skin damage. With a Dfb climate, Thunder Bay experiences distinct seasonal variations that influence UV exposure. As summer peaks, UV levels can soar, reaching a maximum of 8 during midday hours — a reminder to stay vigilant and take necessary precautions to enjoy the sunshine safely. By keeping an eye on the UV Index, residents can make informed choices to enjoy outdoor activities while safeguarding their skin health.
As the sun rises, the UV Index begins its gradual ascent, starting at a mild 1 by 07:00. By 09:00, it nudges up to 2, marking the beginning of greater awareness for sun protection. The intensity peaks at 12:00, with a robust 7, leading to 13:00 and 14:00, where it reaches an impressive 8—the prime time for outdoor activities. As the afternoon light begins to wane, the index dips to 6 by 16:00, and further declines to 4 at 17:00. The evening cools down with a UV Index of 2 by 19:00, reminding us that while sun exposure is crucial for a sunny day, vigilance is key as we enjoy the longer hours of daylight.
| Time | UVI | Category | Time to Burn |
|---|---|---|---|
| 07:00 | 1 | low | 45 min |
| 08:00 | 1 | low | 45 min |
| 09:00 | 2 | low | 45 min |
| 10:00 | 3 | moderate | 30 min |
| 11:00 | 5 | moderate | 30 min |
| 12:00 | 7 | high | 25 min |
| 13:00 | 8 | very high | 15 min |
| 14:00 | 8 | very high | 15 min |
| 15:00 | 7 | high | 25 min |
| 16:00 | 6 | high | 25 min |
| 17:00 | 4 | moderate | 30 min |
| 18:00 | 3 | moderate | 30 min |
| 19:00 | 2 | low | 45 min |
Throughout the year, UV exposure varies significantly, with key changes occurring as seasons shift. The high-risk months for UV exposure are from April to August, where the UV Index reaches very high levels (8-9) in May, June, July, and August, with a burn time as brief as 15 minutes. As summer transitions into fall, UV levels decrease, dropping to moderate categories in October and low levels during the winter months of November and December. Visitors and residents are advised to take extra precautions during the high-risk months by wearing protective clothing, applying sunscreen frequently, and seeking shade to minimize the risk of UV-related harm.
UV Risk Categories
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Edmonton UVI | 2 | 3 | 5 | 6 | 7 | 7 | 8 | 7 | 6 | 4 | 2 | 1 |
| Calgary UVI | 2 | 3 | 4 | 6 | 8 | 8 | 9 | 8 | 7 | 4 | 2 | 1 |
| Thunder Bay | 2 | 3 | 5 | 7 | 8 | 9 | 8 | 8 | 7 | 4 | 2 | 1 |
| Montreal UVI | 2 | 4 | 5 | 7 | 9 | 9 | 8 | 8 | 7 | 5 | 3 | 2 |
| Ottawa UVI | 2 | 4 | 5 | 8 | 9 | 9 | 8 | 8 | 7 | 5 | 3 | 2 |
| Toronto UVI | 2 | 4 | 5 | 8 | 9 | 9 | 9 | 9 | 7 | 5 | 3 | 2 |