Spencer, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 2.2 °C (low) to 13.6 °C (high). Annual precipitation averages 777.5 Millimeters. 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 | -13.7 °C | -3.9 °C | 17.53 mm |
| February | -11.5 °C | -1.6 °C | 20.32 mm |
| March | -4.8 °C | 5.6 °C | 40.13 mm |
| April | 1.7 °C | 14.2 °C | 86.36 mm |
| May | 8.8 °C | 20.8 °C | 107.95 mm |
| June | 14.8 °C | 26.6 °C | 117.09 mm |
| July | 16.7 °C | 28.7 °C | 94.23 mm |
| August | 15.2 °C | 27.3 °C | 93.98 mm |
| September | 10.3 °C | 23.9 °C | 80.77 mm |
| October | 3 °C | 16.1 °C | 59.69 mm |
| November | -4.2 °C | 6.9 °C | 36.07 mm |
| December | -10.3 °C | -0.9 °C | 23.37 mm |
| Annual | 2.2 °C | 13.6 °C | 777.49 mm |
| 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 : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |