Alliston, Ontario climate data is summarized below. Average annual temperatures range from 35.9 °F (low) to 54.6 °F (high). Annual precipitation averages 26.2 Inches. Alliston 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -23.5 °F | -19.1 °F | 177.8 in. |
| February | -24.1 °F | -19.3 °F | 0 in. |
| March | -21 °F | -15.5 °F | 736.6 in. |
| April | -17.5 °F | -11.1 °F | 1270 in. |
| May | -14.2 °F | -6.9 °F | 2006.6 in. |
| June | -11.3 °F | -4.4 °F | 2463.8 in. |
| July | -9.8 °F | -3 °F | 3276.6 in. |
| August | -10.2 °F | -3.5 °F | 2971.8 in. |
| September | -12.6 °F | -5.9 °F | 1600.2 in. |
| October | -15.2 °F | -9.9 °F | 1143 in. |
| November | -18.5 °F | -13.7 °F | 736.6 in. |
| December | -21.2 °F | -17.5 °F | 482.6 in. |
| Annual | 35.9 °F | 54.6 °F | 26.15 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |