Spencer, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 35.9 °F (low) to 56.6 °F (high). Annual precipitation averages 30.6 Inches. Spencer is located in USDA Plant Hardiness Zone 5a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Sep. 21 - Sep. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 7.3 °F | 25.0 °F | 0.69 in. |
| February | 11.3 °F | 29.2 °F | 0.8 in. |
| March | 23.3 °F | 42.1 °F | 1.58 in. |
| April | 35.1 °F | 57.6 °F | 3.4 in. |
| May | 47.8 °F | 69.5 °F | 4.25 in. |
| June | 58.6 °F | 79.9 °F | 4.61 in. |
| July | 62.1 °F | 83.6 °F | 3.71 in. |
| August | 59.3 °F | 81.1 °F | 3.7 in. |
| September | 50.5 °F | 75.0 °F | 3.18 in. |
| October | 37.4 °F | 60.9 °F | 2.35 in. |
| November | 24.5 °F | 44.5 °F | 1.42 in. |
| December | 13.4 °F | 30.3 °F | 0.92 in. |
| Annual | 35.9 °F | 56.6 °F | 30.61 in. |
| Average First Frost Date | Sep. 21 - Sep. 30 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 5a : -20°F to -15°F |
| Plant Hardiness Zone - 2012 | Zone 5a : -20°F to -15°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |