Palmerston, Ontario climate data is summarized below. Average annual temperatures range from 2.2 °C (low) to 11.3 °C (high). Annual precipitation averages 455 Millimeters. Palmerston is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -10.59 °C | -3.46 °C | 0 mm |
| February | -12.16 °C | -3.96 °C | 0 mm |
| March | -6.04 °C | 3.12 °C | 22 mm |
| April | 0.57 °C | 10.9 °C | 30 mm |
| May | 6.96 °C | 18.1 °C | 55 mm |
| June | 11.81 °C | 22.55 °C | 77 mm |
| July | 13.96 °C | 24.81 °C | 90 mm |
| August | 13.66 °C | 24.15 °C | 85 mm |
| September | 9.83 °C | 20.12 °C | 42 mm |
| October | 4.86 °C | 13.13 °C | 27 mm |
| November | -0.94 °C | 6.27 °C | 17 mm |
| December | -6.32 °C | -0.41 °C | 10 mm |
| Annual | 2.2 °C | 11.3 °C | 455 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |