Posen, Michigan has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 33.9 °F (low) to 53.7 °F (high). Annual precipitation averages 31.9 Inches. Posen is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 11.4 °F | 26.5 °F | 1.88 in. |
| February | 10.4 °F | 28.9 °F | 1.45 in. |
| March | 18.0 °F | 38.4 °F | 1.77 in. |
| April | 29.9 °F | 51.0 °F | 3.08 in. |
| May | 41.3 °F | 64.8 °F | 3.05 in. |
| June | 50.9 °F | 74.8 °F | 3.09 in. |
| July | 56.1 °F | 79.0 °F | 3.13 in. |
| August | 55.3 °F | 78.0 °F | 3.27 in. |
| September | 48.5 °F | 70.8 °F | 2.9 in. |
| October | 37.8 °F | 56.7 °F | 3.45 in. |
| November | 28.4 °F | 43.3 °F | 2.65 in. |
| December | 19.2 °F | 32.4 °F | 2.21 in. |
| Annual | 33.9 °F | 53.7 °F | 31.93 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |