Ajax, Ontario climate data is summarized below. Average annual temperatures range from 4.6 °C (low) to 12.8 °C (high). Annual precipitation averages 951 Millimeters. 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 | -7.67 °C | -0.61 °C | 24 mm |
| February | -8.75 °C | -1.01 °C | 26 mm |
| March | -3.15 °C | 5.03 °C | 72 mm |
| April | 2.7 °C | 11.44 °C | 103 mm |
| May | 8.49 °C | 17.85 °C | 96 mm |
| June | 13.8 °C | 22.93 °C | 114 mm |
| July | 16.77 °C | 26.11 °C | 102 mm |
| August | 16.51 °C | 25.49 °C | 104 mm |
| September | 12.29 °C | 21.26 °C | 72 mm |
| October | 6.87 °C | 14.52 °C | 98 mm |
| November | 1.16 °C | 8.24 °C | 72 mm |
| December | -3.66 °C | 2.19 °C | 68 mm |
| Annual | 4.6 °C | 12.8 °C | 951 mm |
| 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 : -20.6°C to -17.8°C |
| Current Drought Conditions | Normal |