Harrow, Ontario climate data is summarized below. Average annual temperatures range from 43.3 °F (low) to 56.1 °F (high). Annual precipitation averages 20.6 Inches. Harrow 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 | -21.6 °F | -18.3 °F | 508 in. |
| February | -22 °F | -18.3 °F | 279.4 in. |
| March | -18.7 °F | -14.4 °F | 1066.8 in. |
| April | -15.5 °F | -10.9 °F | 1320.8 in. |
| May | -12 °F | -7.2 °F | 1524 in. |
| June | -8.6 °F | -4.3 °F | 1651 in. |
| July | -7.3 °F | -3 °F | 1549.4 in. |
| August | -7.5 °F | -3.4 °F | 1524 in. |
| September | -9.8 °F | -5.5 °F | 1270 in. |
| October | -13 °F | -9.1 °F | 889 in. |
| November | -16.4 °F | -13 °F | 990.6 in. |
| December | -19.2 °F | -16.5 °F | 685.8 in. |
| Annual | 43.3 °F | 56.1 °F | 20.55 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 |