Ajax, Ontario climate data is summarized below. Average annual temperatures range from 40.3 °F (low) to 55 °F (high). Annual precipitation averages 37.4 Inches. Ajax is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -22 °F | -18.1 °F | 609.6 in. |
| February | -22.6 °F | -18.3 °F | 660.4 in. |
| March | -19.5 °F | -15 °F | 1828.8 in. |
| April | -16.3 °F | -11.4 °F | 2616.2 in. |
| May | -13.1 °F | -7.9 °F | 2438.4 in. |
| June | -10.1 °F | -5 °F | 2895.6 in. |
| July | -8.5 °F | -3.3 °F | 2590.8 in. |
| August | -8.6 °F | -3.6 °F | 2641.6 in. |
| September | -11 °F | -6 °F | 1828.8 in. |
| October | -14 °F | -9.7 °F | 2489.2 in. |
| November | -17.1 °F | -13.2 °F | 1828.8 in. |
| December | -19.8 °F | -16.6 °F | 1727.2 in. |
| Annual | 40.3 °F | 55 °F | 37.43 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Normal |