Gravenhurst, Ontario climate data is summarized below. Average annual temperatures range from 0.4 °C (low) to 11.4 °C (high). Annual precipitation averages 331 Millimeters. Gravenhurst is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -13.79 °C | -4.14 °C | 3 mm |
| February | -15.1 °C | -4.19 °C | 0 mm |
| March | -8.21 °C | 2.6 °C | 19 mm |
| April | -0.65 °C | 11.18 °C | 24 mm |
| May | 5.68 °C | 19.08 °C | 31 mm |
| June | 11.04 °C | 23.37 °C | 45 mm |
| July | 13.43 °C | 25.63 °C | 61 mm |
| August | 12.64 °C | 24.78 °C | 65 mm |
| September | 8.13 °C | 20.29 °C | 43 mm |
| October | 3.37 °C | 12.98 °C | 22 mm |
| November | -2.52 °C | 5.99 °C | 12 mm |
| December | -8.82 °C | -1.33 °C | 6 mm |
| Annual | 0.4 °C | 11.4 °C | 331 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |