Armstrong, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 6.9 °C (low) to 17.9 °C (high). Annual precipitation averages 1053.9 Millimeters. Armstrong is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.8 °C | 2.8 °C | 42.93 mm |
| February | -4.8 °C | 5.6 °C | 52.58 mm |
| March | 0.7 °C | 12.2 °C | 74.42 mm |
| April | 6.5 °C | 18.3 °C | 113.54 mm |
| May | 12.4 °C | 23.4 °C | 132.59 mm |
| June | 17.5 °C | 28.2 °C | 129.79 mm |
| July | 19.7 °C | 30.6 °C | 113.54 mm |
| August | 18.4 °C | 30 °C | 96.52 mm |
| September | 13.7 °C | 26.1 °C | 95 mm |
| October | 7.6 °C | 19.7 °C | 85.09 mm |
| November | 1.6 °C | 12.1 °C | 68.07 mm |
| December | -3.4 °C | 5.4 °C | 49.78 mm |
| Annual | 6.9 °C | 17.9 °C | 1053.85 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 100-125 Days |
| Plant Hardiness Zone | Zone 6b : -20.6°C to -17.8°C |
| Plant Hardiness Zone - 2012 | Zone 6a : -23.3°C to -20.6°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |