Perth, Ontario climate data is summarized below. Average annual temperatures range from 1.4 °C (low) to 12.1 °C (high). Annual precipitation averages 826 Millimeters. Perth 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 | -13.5 °C | -3.81 °C | 9 mm |
| February | -13.88 °C | -3.42 °C | 7 mm |
| March | -7.69 °C | 3.29 °C | 32 mm |
| April | 0.65 °C | 12.16 °C | 79 mm |
| May | 7.24 °C | 19.94 °C | 92 mm |
| June | 12.48 °C | 24.05 °C | 135 mm |
| July | 14.72 °C | 26.66 °C | 133 mm |
| August | 13.8 °C | 25.75 °C | 111 mm |
| September | 9.13 °C | 21.27 °C | 82 mm |
| October | 3.98 °C | 13.88 °C | 76 mm |
| November | -1.92 °C | 6.83 °C | 42 mm |
| December | -8.79 °C | -1.14 °C | 28 mm |
| Annual | 1.4 °C | 12.1 °C | 826 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 |