| 2023 Hardiness Zone: | Zone 7b: 5°F to 10°F Zone 7a: 0°F to 5°F | |
| 2012 Hardiness Zone: | Zone 6b: -5°F to 0°F 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: | Dfa - Humid Continental Hot Summers | |
| Ecoregion: | 64c - Piedmont Uplands | |
| Current Drought Status: | Exceptional Drought | |
| Heat Zone Days: | 15 - 30 days Over 86°F |
Annual Climate Data for ZIP Code 21104 - Marriottsville, MD | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | Annual |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg Min Temp (°F) | 23 | 24 | 32 | 40 | 50 | 59 | 64 | 63 | 56 | 43 | 35 | 27 | 43 |
| Avg Max Temp (°F) | 41 | 45 | 54 | 66 | 75 | 83 | 87 | 85 | 78 | 67 | 56 | 45 | 65 |
| Avg Precip (In.) | 3.65 | 2.98 | 4.22 | 3.49 | 4.72 | 3.99 | 3.91 | 3.59 | 4.14 | 3.49 | 3.65 | 3.49 | 45.32 |