Monticello, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.3 °C (low) to 13.2 °C (high). Annual precipitation averages 1253.5 Millimeters. Monticello is located in USDA Plant Hardiness Zone 6a. 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 | -10.2 °C | -0.8 °C | 88.39 mm |
| February | -9.7 °C | 0.9 °C | 67.06 mm |
| March | -5.2 °C | 5.6 °C | 93.98 mm |
| April | 0.9 °C | 12.7 °C | 98.3 mm |
| May | 6.9 °C | 19.1 °C | 106.43 mm |
| June | 12 °C | 23.4 °C | 127.25 mm |
| July | 14.3 °C | 26.2 °C | 120.65 mm |
| August | 13.7 °C | 25.1 °C | 113.79 mm |
| September | 9.7 °C | 21.3 °C | 123.19 mm |
| October | 3.7 °C | 14.6 °C | 118.87 mm |
| November | -1.9 °C | 7.9 °C | 89.41 mm |
| December | -6.4 °C | 1.9 °C | 106.17 mm |
| Annual | 2.3 °C | 13.2 °C | 1253.49 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°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 |