Lewiston, Maine has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 2.3 °C (low) to 13.1 °C (high). Annual precipitation averages 1179.1 Millimeters. Lewiston 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.9 °C | -1.4 °C | 81.03 mm |
| February | -11 °C | 0.2 °C | 80.77 mm |
| March | -5.4 °C | 4.9 °C | 94.49 mm |
| April | 0.7 °C | 11.8 °C | 109.47 mm |
| May | 6.7 °C | 18.5 °C | 87.38 mm |
| June | 12.2 °C | 23.3 °C | 113.54 mm |
| July | 15.3 °C | 26.7 °C | 90.42 mm |
| August | 14.6 °C | 26.1 °C | 84.33 mm |
| September | 10.3 °C | 21.9 °C | 96.77 mm |
| October | 4.2 °C | 14.6 °C | 127.51 mm |
| November | -1.3 °C | 7.9 °C | 103.63 mm |
| December | -7.2 °C | 2.1 °C | 109.73 mm |
| Annual | 2.3 °C | 13.1 °C | 1179.07 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 5b : -26.1°C to -23.3°C |
| Plant Hardiness Zone - 2012 | Zone 5b : -26.1°C to -23.3°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |