Grimsby, Ontario climate data is summarized below. Average annual temperatures range from 4.9 °C (low) to 13.4 °C (high). Annual precipitation averages 899 Millimeters. Grimsby is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -7.4 °C | -0.58 °C | 40 mm |
| February | -8.63 °C | -1.08 °C | 38 mm |
| March | -2.84 °C | 5.44 °C | 83 mm |
| April | 2.58 °C | 12.28 °C | 97 mm |
| May | 8.38 °C | 19.26 °C | 92 mm |
| June | 14.28 °C | 24.4 °C | 87 mm |
| July | 17.21 °C | 27.13 °C | 83 mm |
| August | 16.82 °C | 26.18 °C | 78 mm |
| September | 12.71 °C | 21.7 °C | 72 mm |
| October | 7.26 °C | 14.96 °C | 92 mm |
| November | 1.39 °C | 8.54 °C | 63 mm |
| December | -3.35 °C | 2.43 °C | 74 mm |
| Annual | 4.9 °C | 13.4 °C | 899 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Normal |