| 2023 Hardiness Zone: | Zone 6a: -10°F to -5°F |
| 2012 Hardiness Zone: | Zone 6a: -10°F to -5°F Zone 5b: -15°F to -10°F |
| 1990 Hardiness Zone: | Zone 6a: -10F to -5F |
| 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: | 69a - Forested Hills and Mountains |
| Heat Zone Days: | Rare Over 86°F |
Annual Climate Data for ZIP Code 21541 - Mc Henry, MD | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 17 | 18 | 26 | 34 | 45 | 53 | 57 | 56 | 50 | 39 | 30 | 21 | 37 |
| Avg Max Temp (°F) | 33 | 36 | 45 | 56 | 66 | 73 | 76 | 75 | 69 | 59 | 47 | 37 | 56 |
| Avg Precip (In.) | 4.35 | 3.98 | 4.94 | 4.57 | 5.29 | 5 | 5.54 | 4.79 | 3.68 | 3.31 | 4.05 | 4.31 | 53.81 |