Westerlo, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 34.4 °F (low) to 56.3 °F (high). Annual precipitation averages 44.5 Inches. Westerlo is located in USDA Plant Hardiness Zone 5b. 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 | 11.2 °F | 31.0 °F | 2.96 in. |
| February | 12.4 °F | 33.4 °F | 2.47 in. |
| March | 20.1 °F | 41.6 °F | 3.31 in. |
| April | 31.7 °F | 55.4 °F | 3.62 in. |
| May | 43.4 °F | 67.6 °F | 3.48 in. |
| June | 52.1 °F | 75.4 °F | 4.66 in. |
| July | 56.6 °F | 79.9 °F | 4.1 in. |
| August | 54.8 °F | 78.1 °F | 4.3 in. |
| September | 47.4 °F | 71.2 °F | 4.05 in. |
| October | 36.9 °F | 58.9 °F | 4.78 in. |
| November | 27.8 °F | 47.2 °F | 3.19 in. |
| December | 18.4 °F | 36.0 °F | 3.58 in. |
| Annual | 34.4 °F | 56.3 °F | 44.5 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 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |