| 2023 Hardiness Zone: | Zone 7b: 5°F to 10°F | |
| 2012 Hardiness Zone: | Zone 7a: 0°F to 5°F | |
| 1990 Hardiness Zone: | Zone 6b: -5F to 0F | |
| Average First Frost Date: | Oct. 21 - Oct. 31 | |
| Average Last Frost Date: | Apr. 21 - Apr. 30 | |
| Koppen-Geiger Climate Zone: | Cfa - Humid Subtropical Climate | |
| Ecoregion: | 64c - Piedmont Uplands | |
| Current Drought Status: | Exceptional Drought | |
| Heat Zone Days: | 15 - 30 days Over 86°F |
Annual Climate Data for ZIP Code 21057 - Glen Arm, MD | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 24 | 26 | 33 | 42 | 52 | 61 | 66 | 65 | 58 | 46 | 36 | 28 | 45 |
| Avg Max Temp (°F) | 41 | 45 | 55 | 65 | 75 | 83 | 87 | 86 | 79 | 68 | 56 | 46 | 66 |
| Avg Precip (In.) | 3.79 | 3.12 | 4.42 | 3.7 | 5.09 | 4.12 | 4.49 | 4.34 | 4.56 | 3.74 | 3.89 | 3.77 | 49.03 |