Armstrong, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 36.1 °F (low) to 55.8 °F (high). Annual precipitation averages 32.3 Inches. Armstrong 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 Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 7.3 °F | 24.0 °F | 0.79 in. |
| February | 11.2 °F | 28.3 °F | 0.9 in. |
| March | 23.4 °F | 41.1 °F | 1.76 in. |
| April | 35.3 °F | 56.9 °F | 3.39 in. |
| May | 47.9 °F | 69.4 °F | 4.51 in. |
| June | 59.0 °F | 79.5 °F | 4.95 in. |
| July | 62.3 °F | 82.4 °F | 4.06 in. |
| August | 59.6 °F | 80.0 °F | 3.75 in. |
| September | 51.1 °F | 74.4 °F | 3.19 in. |
| October | 38.0 °F | 60.3 °F | 2.4 in. |
| November | 25.0 °F | 43.4 °F | 1.39 in. |
| December | 13.6 °F | 29.3 °F | 1.18 in. |
| Annual | 36.1 °F | 55.8 °F | 32.27 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 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 |