Last updated: June 2, 2025
Understanding the UV Index is crucial for residents of Thunder Bay, Canada, as it helps in safeguarding skin health and preventing sunburns. With a continental climate (Dfb), Thunder Bay experiences varying UV levels throughout the year, making awareness essential. For instance, during the summer months, midday UV Index values can soar, peaking at 9—indicating a high risk of harm from unprotected sun exposure. By staying informed about UV levels, you can enjoy the beautiful outdoors while ensuring your skin remains protected and healthy.
From 07:00 to 09:00, the UV Index remains low, peaking at 2, making it a gentle start to the day for outdoor activities. As the clock strikes 10:00, the intensity ramps up quickly, soaring to 4. The sun reaches its zenith around 12:00 with an impressive peak of 7, signaling a need for sun protection. The afternoon brings even higher values, with the UV Index hitting its maximum at 14:00 with a blazing 9. As the day progresses, a gradual decline follows, dropping to 5 by 17:00 and tapering off to a comfortable 2 by 19:00. It’s a vivid reminder to stay sun-smart during the midday hours when UV exposure is at its highest!
| 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 | 4 | moderate | 30 min |
| 11:00 | 6 | high | 25 min |
| 12:00 | 7 | high | 25 min |
| 13:00 | 8 | very high | 15 min |
| 14:00 | 9 | very high | 15 min |
| 15:00 | 8 | very high | 15 min |
| 16:00 | 7 | high | 25 min |
| 17:00 | 5 | 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 |