Grinnell, Kansas has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.7 °C (low) to 19.1 °C (high). Annual precipitation averages 548.1 Millimeters. Grinnell is located in USDA Plant Hardiness Zone 6a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -8.6 °C | 5.9 °C | 10.16 mm |
| February | -7.2 °C | 7.7 °C | 15.49 mm |
| March | -2.8 °C | 13.4 °C | 29.21 mm |
| April | 2.1 °C | 18.2 °C | 49.02 mm |
| May | 8.4 °C | 23.6 °C | 82.55 mm |
| June | 14.5 °C | 30 °C | 72.39 mm |
| July | 17.4 °C | 32.7 °C | 93.22 mm |
| August | 16.4 °C | 31.3 °C | 75.95 mm |
| September | 11.3 °C | 27.2 °C | 43.43 mm |
| October | 3.8 °C | 20 °C | 42.16 mm |
| November | -2.9 °C | 12.5 °C | 17.78 mm |
| December | -7.7 °C | 6.6 °C | 16.76 mm |
| Annual | 3.7 °C | 19.1 °C | 548.12 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 6a : -23.3°C to -20.6°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 |