Middlesex, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 3 °C (low) to 13.6 °C (high). Annual precipitation averages 921 Millimeters. Middlesex is located in USDA Plant Hardiness Zone 6b. 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 | -9.2 °C | -0.3 °C | 56.64 mm |
| February | -8.8 °C | 0.9 °C | 48.01 mm |
| March | -5.1 °C | 5.3 °C | 65.79 mm |
| April | 0.8 °C | 12.7 °C | 75.44 mm |
| May | 7.2 °C | 19.7 °C | 81.28 mm |
| June | 12.4 °C | 24.2 °C | 87.63 mm |
| July | 15 °C | 26.3 °C | 98.04 mm |
| August | 14.2 °C | 25.6 °C | 91.44 mm |
| September | 10.7 °C | 22.1 °C | 89.92 mm |
| October | 4.7 °C | 15.3 °C | 92.71 mm |
| November | -0.6 °C | 8.4 °C | 69.09 mm |
| December | -5.4 °C | 2.7 °C | 65.02 mm |
| Annual | 3 °C | 13.6 °C | 921.01 mm |
| 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 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |