Dexter, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 39 °F (low) to 59.9 °F (high). Annual precipitation averages 35.4 Inches. Dexter is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 11.9 °F | 30.0 °F | 0.89 in. |
| February | 16.1 °F | 35.1 °F | 1.18 in. |
| March | 26.7 °F | 47.9 °F | 2.03 in. |
| April | 38.0 °F | 61.3 °F | 3.67 in. |
| May | 50.0 °F | 71.5 °F | 5.01 in. |
| June | 60.2 °F | 80.9 °F | 5.1 in. |
| July | 64.2 °F | 84.7 °F | 4.19 in. |
| August | 61.6 °F | 83.0 °F | 4.02 in. |
| September | 52.8 °F | 76.7 °F | 3.51 in. |
| October | 40.4 °F | 63.9 °F | 2.69 in. |
| November | 28.2 °F | 48.2 °F | 1.82 in. |
| December | 17.5 °F | 35.0 °F | 1.32 in. |
| Annual | 39 °F | 59.9 °F | 35.43 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 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 | Dfa - Humid Continental Hot Summers With Year Around Precipitation |