Foster, Missouri has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 7.2 °C (low) to 19.3 °C (high). Annual precipitation averages 1108.2 Millimeters. Foster is located in USDA Plant Hardiness Zone 6b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -6.1 °C | 5.1 °C | 39.88 mm |
| February | -4.1 °C | 7.9 °C | 49.28 mm |
| March | 1.1 °C | 13.7 °C | 73.66 mm |
| April | 6.6 °C | 19.4 °C | 116.33 mm |
| May | 12.6 °C | 24.3 °C | 155.45 mm |
| June | 18 °C | 29.2 °C | 140.97 mm |
| July | 20.3 °C | 31.9 °C | 113.54 mm |
| August | 19.1 °C | 31.4 °C | 97.54 mm |
| September | 14.1 °C | 27.3 °C | 111.25 mm |
| October | 7.5 °C | 20.9 °C | 88.14 mm |
| November | 1.3 °C | 13.4 °C | 69.6 mm |
| December | -3.8 °C | 7.1 °C | 52.58 mm |
| Annual | 7.2 °C | 19.3 °C | 1108.22 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| 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 |