| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 6b: -5°F to 0°F |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 5b: -15°F to -10°F |
| 1990 Hardiness Zone: | Zone 1b: -15F to -10F |
| Average First Frost Date: | Oct. 1 - Oct. 10 |
| Average Last Frost Date: | May 11 - May 20 |
| Koppen-Geiger Climate Zone: | Dfb - Humid Continental Mild Summer, Wet All Year |
| Ecoregion: | 61c - Low Lime Drift Plain |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 16159 - West Middlesex, PA | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 18 | 19 | 27 | 36 | 46 | 55 | 59 | 58 | 51 | 40 | 33 | 24 | 39 |
| Avg Max Temp (°F) | 35 | 38 | 49 | 61 | 72 | 80 | 84 | 82 | 76 | 64 | 51 | 40 | 61 |
| Avg Precip (In.) | 2.42 | 2.11 | 3.01 | 3.31 | 3.59 | 4.35 | 4.14 | 3.63 | 3.92 | 2.67 | 3.28 | 2.92 | 39.36 |