Fort Severn, Ontario climate data is summarized below. Annual precipitation averages 415 Millimeters. Fort Severn is located in USDA Plant Hardiness Zone 1a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Aug. 11 - Aug. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -27.22 °C | -19.13 °C | 0 mm |
| February | -27.69 °C | -17.38 °C | 0 mm |
| March | -22.63 °C | -11.14 °C | 0 mm |
| April | -12.91 °C | -2.84 °C | 0 mm |
| May | -4.11 °C | 4.54 °C | 28 mm |
| June | 2.4 °C | 13.75 °C | 60 mm |
| July | 6.59 °C | 17.23 °C | 97 mm |
| August | 7.92 °C | 16.58 °C | 97 mm |
| September | 4.79 °C | 12.25 °C | 81 mm |
| October | 0.02 °C | 4.67 °C | 52 mm |
| November | -10.31 °C | -4.3 °C | 0 mm |
| December | -21.14 °C | -14.55 °C | 0 mm |
| Annual | -8.7 °C | -0 °C | 415 mm |
| Average First Frost Date | Aug. 11 - Aug. 20 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 1a : |
| Current Drought Conditions | Normal |