Harrietta, Michigan has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 34.3 °F (low) to 54.8 °F (high). Annual precipitation averages 36.4 Inches. Harrietta is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 21 - May 31 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 12.3 °F | 27.1 °F | 2.41 in. |
| February | 12.0 °F | 30.0 °F | 1.8 in. |
| March | 19.3 °F | 40.5 °F | 2.15 in. |
| April | 30.5 °F | 53.6 °F | 3.4 in. |
| May | 42.2 °F | 66.9 °F | 3.52 in. |
| June | 51.9 °F | 76.4 °F | 3.55 in. |
| July | 55.9 °F | 80.2 °F | 3.29 in. |
| August | 54.8 °F | 78.4 °F | 3.3 in. |
| September | 47.5 °F | 71.1 °F | 3.34 in. |
| October | 37.2 °F | 57.3 °F | 4.08 in. |
| November | 28.0 °F | 43.3 °F | 3.07 in. |
| December | 19.5 °F | 32.3 °F | 2.48 in. |
| Annual | 34.3 °F | 54.8 °F | 36.39 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 21 - May 31 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |