Marietta, Ohio has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 42.3 °F (low) to 64.5 °F (high). Annual precipitation averages 44.1 Inches. Marietta is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 21.6 °F | 39.5 °F | 3.3 in. |
| February | 23.1 °F | 43.0 °F | 3.06 in. |
| March | 30.0 °F | 52.6 °F | 4.01 in. |
| April | 40.4 °F | 66.5 °F | 3.79 in. |
| May | 50.6 °F | 74.8 °F | 4.36 in. |
| June | 59.8 °F | 82.3 °F | 4.7 in. |
| July | 63.4 °F | 85.7 °F | 4.72 in. |
| August | 62.5 °F | 85.0 °F | 3.64 in. |
| September | 54.8 °F | 78.7 °F | 3.38 in. |
| October | 42.4 °F | 67.2 °F | 2.82 in. |
| November | 32.8 °F | 54.7 °F | 2.93 in. |
| December | 26.7 °F | 44.2 °F | 3.4 in. |
| Annual | 42.3 °F | 64.5 °F | 44.11 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -5°F to 0°F |
| Plant Hardiness Zone - 2012 | Zone 6b : -5°F to 0°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |