The climate of Thunder Bay is influenced by Lake Superior, resulting in cooler summer temperatures and warmer winter temperatures. So when visiting, it’s important to pack for cooler weather and plan to wear layers that can easily accodate the temperature for that part of the day.

The average daily temperatures range from a high of 62 F/17.6 °C in July and a low of 5°F/-14.8 °C in January; the average daily high in July is 75°F/24.2 °C and the average daily high in January is 17°F/-8.6 °C. Summer daytime temperatures vary from 15° C to 30° C, while nights tend to be cooler and less humid than southern locations.

The summer period is well suited to both active and passive outdoor recreational pursuits. Recent winter daytime temperatures have ranged from springlike to relatively cold with sunny days. This type of climate is well suited to all kinds of active outdoor recreational pursuits. Spring and autumn are short with cool days and evenings.

Winter outdoor recreation often extends well into April while summer culminates in a spectacular show of colours in the fall.Precipitation is highly variable from year to year. The annual average rainfall is 527.3 mm while the average snowfall is 213 cm.
On average, Thunder Bay is the sunniest location in eastern, sunnier than any city in Canada located to the east of it.

Thunder Bay Weather Forecast

5 Day Weather Forecast

Thursday night Friday Friday night Cloudy Low 8°C Sunny with cloudy periods High 22°C A few clouds High 22°C Saturday Sunday Monday Sunny High 25°C Sunny High 24°C Chance of showers High 20°C

Detailed Thunder Bay Weather Forecast

Thunder Bay Airport 6:00 PM EDT Thursday 02 July 2009

Thursday night Cloudy. Becoming cloudy periods near midnight. Low 8. Friday Sunny with cloudy periods. Wind becoming northwest 20 km/h in the afternoon. High 22. UV index 8 or very high. Friday night A few clouds. Wind northwest 20 km/h becoming light near midnight. Low 7. Saturday Sunny. High 25. Sunday Sunny. Low 10. High 24. Monday A mix of sun and cloud with 40 percent chance of showers. Low 7. High 20.