Fort Severn, Ontario climate data is summarized below. Average annual temperatures range from 16.4 °F (low) to 32 °F (high). Annual precipitation averages 16.3 Inches. 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 | -32.9 °F | -28.4 °F | 0 in. |
| February | -33.2 °F | -27.4 °F | 0 in. |
| March | -30.4 °F | -24 °F | 0 in. |
| April | -25 °F | -19.4 °F | 0 in. |
| May | -20.1 °F | -15.3 °F | 711.2 in. |
| June | -16.4 °F | -10.1 °F | 1524 in. |
| July | -14.1 °F | -8.2 °F | 2463.8 in. |
| August | -13.4 °F | -8.6 °F | 2463.8 in. |
| September | -15.1 °F | -11 °F | 2057.4 in. |
| October | -17.8 °F | -15.2 °F | 1320.8 in. |
| November | -23.5 °F | -20.2 °F | 0 in. |
| December | -29.5 °F | -25.9 °F | 0 in. |
| Annual | 16.4 °F | 32 °F | 16.34 in. |
| 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 : -60°F to -55°F |
| Current Drought Conditions | Normal |