McLean, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.4 °C (low) to 13.3 °C (high). Annual precipitation averages 1078.5 Millimeters. McLean 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 | -10.1 °C | -0.6 °C | 68.33 mm |
| February | -9.4 °C | 0.6 °C | 56.64 mm |
| March | -5.7 °C | 4.8 °C | 78.99 mm |
| April | 0.7 °C | 12.3 °C | 90.42 mm |
| May | 6.9 °C | 19.4 °C | 90.17 mm |
| June | 12.1 °C | 24 °C | 111.51 mm |
| July | 14.4 °C | 26.4 °C | 106.93 mm |
| August | 13.7 °C | 25.8 °C | 104.14 mm |
| September | 9.4 °C | 22 °C | 107.7 mm |
| October | 3.8 °C | 14.9 °C | 103.38 mm |
| November | -0.9 °C | 8.2 °C | 83.57 mm |
| December | -6 °C | 2.2 °C | 76.71 mm |
| Annual | 2.4 °C | 13.3 °C | 1078.49 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |