McLennan, Alberta climate data is summarized below. Average annual temperatures range from -3.5 °C (low) to 7 °C (high). Annual precipitation averages 432 Millimeters. McLennan is located in USDA Plant Hardiness Zone 3a. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -16.86 °C | -8.34 °C | 0 mm |
| February | -15.12 °C | -5.72 °C | 0 mm |
| March | -11.74 °C | -0.91 °C | 0 mm |
| April | -3.32 °C | 7.62 °C | 27 mm |
| May | 3.08 °C | 16.52 °C | 60 mm |
| June | 8.13 °C | 20.17 °C | 96 mm |
| July | 10.37 °C | 22.52 °C | 101 mm |
| August | 8.94 °C | 21.48 °C | 62 mm |
| September | 4.25 °C | 16.43 °C | 46 mm |
| October | -0.75 °C | 7.88 °C | 40 mm |
| November | -9.71 °C | -3.04 °C | 0 mm |
| December | -18.86 °C | -10.54 °C | 0 mm |
| Annual | -3.5 °C | 7 °C | 432 mm |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | Over 180 Days |
| Plant Hardiness Zone | Zone 3a : -40°C to -37.2°C |
| Current Drought Conditions | Normal |