| Climate data for Fort Smith (Fort Smith Airport) WMO ID: 71934; coordinates 60°01′13″N 111°57′43″W / 60 °N 111 °W / 60 ; -111 (Fort Smith Airport); elevation: 205 m (673 ft); 1991−2020 normals, extremes 1913−present |
| Month | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov |
| Record high humidex | 8 | 11 | 16 | 29 | 32 | 38 | 41 | 38 | 31 | 25 | 12 |
| Record high °C (°F) | 8 (47 ) | 9 (49 ) | 16 (62 ) | 24 (75 ) | 31 (87 ) | 39 (103 ) | 39 (102 ) | 33 (93 ) | 29 (84 ) | 24 (76 ) | 12 (53 ) |
| Mean daily maximum °C (°F) | −17 (0 ) | −13 (8 ) | −5 (22 ) | 5 (42 ) | 14 (58 ) | 21 (70 ) | 23 (74 ) | 21 (70 ) | 14 (57 ) | 4 (39 ) | −7 (19 ) |
| Daily mean °C (°F) | −21 (−7 ) | −18 (−1 ) | −11 (10 ) | −0 (30 ) | 8 (46 ) | 15 (59 ) | 17 (63 ) | 15 (59 ) | 8 (48 ) | 0 (32 ) | −10 (12 ) |
| Mean daily minimum °C (°F) | −26 (−15 ) | −24 (−11 ) | −18 (−1 ) | −7 (19 ) | 1 (34 ) | 8 (47 ) | 11 (52 ) | 9 (48 ) | 3 (38 ) | −3 (26 ) | −14 (6 ) |
| Record low °C (°F) | −49 (−56 ) | −53 (−65 ) | −44 (−47 ) | −40 (−41 ) | −23 (−9 ) | −6 (21 ) | −3 (26 ) | −5 (21 ) | −12 (9 ) | −27 (−18 ) | −40 (−41 ) |
| Record low wind chill | −60 | −58 | −55 | −50 | −26 | −8 | 0 | −4 | −17 | −35 | −48 |
| Average precipitation mm (inches) | 17 (0 ) | 12 (0 ) | 14 (0 ) | 13 (0 ) | 27 (1 ) | 47 (1 ) | 58 (2 ) | 57 (2 ) | 42 (1 ) | 30 (1 ) | 21 (0 ) |
| Average rainfall mm (inches) | 0 (0 ) | 0 (0 ) | 0 (0 ) | 6 (0 ) | 22 (0 ) | 48 (1 ) | 60 (2 ) | 61 (2 ) | 45 (1 ) | 15 (0 ) | 1 (0 ) |
| Average snowfall cm (inches) | 24 (9 ) | 17 (6 ) | 17 (6 ) | 7 (3 ) | 5 (2 ) | 0 (0 ) | 0 (0 ) | 0 (0 ) | 0 (0 ) | 18 (7 ) | 29 (11 ) |
| Average precipitation days (≥ 0 mm) | 13 | 10 | 10 | 7 | 9 | 10 | 12 | 13 | 12 | 14 | 13 |
| Average rainy days (≥ 0 mm) | 0 | 0 | 0 | 2 | 6 | 10 | 12 | 13 | 12 | 8 | 1 |
| Average snowy days (≥ 0 cm) | 12 | 10 | 8 | 3 | 1 | 0 | 0 | 0 | 0 | 8 | 14 |
| Average relative humidity (%) (at 1500 LST) | 78 | 74 | 62 | 47 | 40 | 43 | 48 | 52 | 56 | 71 | 83 |
| Mean monthly sunshine hours | 57 | 113 | 176 | 243 | 285 | 299 | 301 | 261 | 132 | 87 | 43 |
| Source: Environment and Climate Change Canada (June maximum) (December minimum) (sun 1951–1980) |