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Climate

Thunder Bay experiences very diverse weather, enjoying each of the four seasons in all their richness. The city feels the heat in the summertime, the frost in the winter, and the ambiguity of those transitioning months.

Spring/Summer
The warmer months start later in the year in Thunder Bay compared to most Ontario cities. Temperatures begin to rise in April and May, melting the snow and unthawing the lakes. The summer months are typically characterized by long, sunny days and cool evenings. Daylight in July, August, and September lasts as long as 16 hours. Summertime in Thunder Bay is well-suited to outdoor recreation and sports such as golf, hiking, swimming, sailing, cycling, and boating.

Summers are often more comfortable in Thunder Bay than many southern cities because of low humidity and cooler nights.

Fall
Possibly the most beautiful time of the year, the autumn season in Thunder Bay is stunning. The region’s bountiful trees become coloured with red, gold, and rust coloured leaves. The air is cool and crisp and the sun shines. It is the perfect weather for nature walks and hikes.

Winter
Thunder Bay experiences winter weather typical of Northwestern Ontario and other northern regions – shorter days and cold temperatures with a high incidence of sunshine. The colder months bring plenty of snow and are very conducive to winter recreation. Activities such as skiing, snowboarding, snowshoeing, dogsledding, ice fishing and snow-machining are a favourite among locals and visitors. The winter season will usually start in November and continue until Spring time.

Climate Data - Average Weather - Metric
 Statistics     Units  Jan  Feb  Mar  Apr   May Jun 
 Temperature
 Mean Value
 F
 C
 5
 -15.0     
 9
 -12.8     
 21.9 
 -5.6          
 36.9
 2.7         
 48.2
 9.0       
 57
 13.9    
 High Temperature
 Mean Value
 F
 C
 16
-8.9
 20.8
 -6.2
 32.4
 0.2
 47.7
 8.7
 60.3 
 15.7
 68.9 
 20.5
 Low Temperature
 Mean Value
 F
 C
 -6.3
 -21.3
 -3.1 
 -19.5
 11.1
 -11.6
 26.1 
 -3.3
 36 
 2.2
 45 
 7.2
 Precipitation
 Mean Monthly Value
 Inches
 mm
 1.3
 32.4
 1 
 25.6
 1.7
 40.9 
 1.9 
 47.1
 2.8 
 69.3
 3.4
 84.0 
 Snowfall
 Mean Monthly Value
 Inches 
 cm
 18
 43.3
 11.9
  28.5
11.9 
 28.5
 6.2 
 14.8
 0.9 
 2.2
 0 
 0.0

 

Climate Data - Average Weather - English Units and Metric
 Statistics     Units  Jul Aug  Sep Oct Nov   Dec Avg
 Temperature 
 Mean Value
 F
 C
 63.9    
 17.7
 61.5    
 16.4
 52.2    
 11.2
 41.7    
 5.4
 27.3    
 -2.6
 11.7    
  -11.3  
 36.4    
 2.42
 High  Temperature
 Mean Value
 F
 C
 75.9
 24.4
 73.2
 22.9
 63.1
 17.3
 51.4
 10.8
 35.6
 2.0
 21.2
 -6.0
 47.2
 8.45
 Low  Temperature
 Mean Value
 F
 C
 51.8
 11.0
 50
 10.0
 41.2
 5.1
 31.8
 -0.1
 18.7
 -7.4
 1.9
 -16.7
 25.3
 -3.7
 Precipitation 
 Mean Monthly Value
 Inches
 mm
 3.3
 79.9
 3.6
 88.5
 3.5
 86.4
 2.5
 60.9
 2
 49.4
 1.6
 39.3
 2.4
 58.64
 Snowfall 
 Mean Monthly Value
 Inches
 cm
 0
 0.0
 0
 0.0
 0.2
 0.4
 2
 4.9
 11
 26.5
 19.3
 46.4
 6.8
 16.29