Grimsby, Ontario climate data is summarized below. Average annual temperatures range from 40.8 °F (low) to 56.1 °F (high). Annual precipitation averages 35.4 Inches. 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 | -21.9 °F | -18.1 °F | 1016 in. |
| February | -22.6 °F | -18.4 °F | 965.2 in. |
| March | -19.4 °F | -14.8 °F | 2108.2 in. |
| April | -16.3 °F | -11 °F | 2463.8 in. |
| May | -13.1 °F | -7.1 °F | 2336.8 in. |
| June | -9.8 °F | -4.2 °F | 2209.8 in. |
| July | -8.2 °F | -2.7 °F | 2108.2 in. |
| August | -8.4 °F | -3.2 °F | 1981.2 in. |
| September | -10.7 °F | -5.7 °F | 1828.8 in. |
| October | -13.7 °F | -9.5 °F | 2336.8 in. |
| November | -17 °F | -13 °F | 1600.2 in. |
| December | -19.6 °F | -16.4 °F | 1879.6 in. |
| Annual | 40.8 °F | 56.1 °F | 35.39 in. |
| 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 : 0°F to 5°F |
| Current Drought Conditions | Normal |