Smiths Falls, Ontario climate data is summarized below. Average annual temperatures range from 1.6 °C (low) to 12.2 °C (high). Annual precipitation averages 831 Millimeters. Smiths Falls is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -13.05 °C | -3.73 °C | 10 mm |
| February | -13.3 °C | -3.3 °C | 8 mm |
| March | -7.02 °C | 3.55 °C | 37 mm |
| April | 0.97 °C | 12.22 °C | 82 mm |
| May | 7.41 °C | 19.85 °C | 94 mm |
| June | 12.57 °C | 23.96 °C | 127 mm |
| July | 14.82 °C | 26.58 °C | 140 mm |
| August | 13.94 °C | 25.73 °C | 99 mm |
| September | 9.3 °C | 21.34 °C | 83 mm |
| October | 4.07 °C | 14.01 °C | 75 mm |
| November | -1.8 °C | 6.94 °C | 46 mm |
| December | -8.55 °C | -1.03 °C | 30 mm |
| Annual | 1.6 °C | 12.2 °C | 831 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |