Olean, New York has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 1.9 °C (low) to 14 °C (high). Annual precipitation averages 1042.2 Millimeters. Olean 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 Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -9.8 °C | -0.1 °C | 71.37 mm |
| February | -9.5 °C | 1.3 °C | 51.82 mm |
| March | -5.9 °C | 6.2 °C | 68.83 mm |
| April | -0.1 °C | 13.6 °C | 85.6 mm |
| May | 6.1 °C | 20.4 °C | 93.47 mm |
| June | 10.9 °C | 24.7 °C | 113.54 mm |
| July | 13.3 °C | 26.7 °C | 110.24 mm |
| August | 12.9 °C | 25.9 °C | 103.63 mm |
| September | 9.1 °C | 22.3 °C | 99.06 mm |
| October | 3.1 °C | 15.5 °C | 91.44 mm |
| November | -1.7 °C | 8.4 °C | 75.18 mm |
| December | -6 °C | 2.6 °C | 77.98 mm |
| Annual | 1.9 °C | 14 °C | 1042.16 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |