Lanark, Ontario climate data is summarized below. Average annual temperatures range from 34.3 °F (low) to 53.5 °F (high). Annual precipitation averages 29.2 Inches. Lanark is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -25.3 °F | -20 °F | 127 in. |
| February | -25.4 °F | -19.7 °F | 76.2 in. |
| March | -22 °F | -16.2 °F | 635 in. |
| April | -17.5 °F | -11.1 °F | 1524 in. |
| May | -13.8 °F | -6.7 °F | 2032 in. |
| June | -10.9 °F | -4.5 °F | 3022.6 in. |
| July | -9.7 °F | -3.1 °F | 3505.2 in. |
| August | -10.2 °F | -3.6 °F | 2895.6 in. |
| September | -12.8 °F | -6.1 °F | 1955.8 in. |
| October | -15.6 °F | -10.2 °F | 1625.6 in. |
| November | -18.9 °F | -14.1 °F | 863.6 in. |
| December | -22.8 °F | -18.5 °F | 558.8 in. |
| Annual | 34.3 °F | 53.5 °F | 29.18 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Normal |