Glassmanor, Maryland has a Humid Subtropical Climate climate (Köppen classification: Cfa). Average annual temperatures range from 9.4 °C (low) to 19.4 °C (high). Annual precipitation averages 1147.1 Millimeters. Glassmanor is located in USDA Plant Hardiness Zone 8a. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -2.1 °C | 6.7 °C | 77.98 mm |
| February | -1.3 °C | 8.6 °C | 67.56 mm |
| March | 2.6 °C | 13.1 °C | 97.54 mm |
| April | 8.2 °C | 19.4 °C | 87.12 mm |
| May | 13.5 °C | 24.1 °C | 113.03 mm |
| June | 18.7 °C | 28.9 °C | 116.08 mm |
| July | 21.3 °C | 31.4 °C | 118.11 mm |
| August | 20.3 °C | 30.4 °C | 92.96 mm |
| September | 16.7 °C | 26.7 °C | 107.95 mm |
| October | 10.1 °C | 20.3 °C | 97.03 mm |
| November | 4.3 °C | 14.2 °C | 77.22 mm |
| December | 0.3 °C | 9 °C | 94.49 mm |
| Annual | 9.4 °C | 19.4 °C | 1147.07 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8a : -12.2°C to -9.4°C |
| Plant Hardiness Zone - 2012 | Zone 7b : -15°C to -12.2°C |
| Current Drought Conditions | Severe Drought |
| Köppen Climate Classification | Cfa - Humid Subtropical Climate |