Perth, Ontario climate data is summarized below. Average annual temperatures range from 34.4 °F (low) to 53.8 °F (high). Annual precipitation averages 32.5 Inches. 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 | -25.3 °F | -19.9 °F | 228.6 in. |
| February | -25.5 °F | -19.7 °F | 177.8 in. |
| March | -22.1 °F | -16 °F | 812.8 in. |
| April | -17.4 °F | -11 °F | 2006.6 in. |
| May | -13.8 °F | -6.7 °F | 2336.8 in. |
| June | -10.8 °F | -4.4 °F | 3429 in. |
| July | -9.6 °F | -3 °F | 3378.2 in. |
| August | -10.1 °F | -3.5 °F | 2819.4 in. |
| September | -12.7 °F | -6 °F | 2082.8 in. |
| October | -15.6 °F | -10.1 °F | 1930.4 in. |
| November | -18.8 °F | -14 °F | 1066.8 in. |
| December | -22.7 °F | -18.4 °F | 711.2 in. |
| Annual | 34.4 °F | 53.8 °F | 32.51 in. |
| 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 : -15°F to -10°F |
| Current Drought Conditions | Normal |