Grand Junction, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.3 °C (low) to 15 °C (high). Annual precipitation averages 898.4 Millimeters. Grand Junction 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 | -12.1 °C | -2.1 °C | 23.11 mm |
| February | -9.7 °C | 0.6 °C | 29.46 mm |
| March | -3.3 °C | 8 °C | 51.05 mm |
| April | 2.8 °C | 16.1 °C | 95.25 mm |
| May | 9.7 °C | 21.9 °C | 126.49 mm |
| June | 15.4 °C | 27.1 °C | 133.86 mm |
| July | 17.4 °C | 29.1 °C | 107.95 mm |
| August | 16 °C | 27.9 °C | 104.39 mm |
| September | 11 °C | 24.7 °C | 81.53 mm |
| October | 4.1 °C | 17.5 °C | 66.29 mm |
| November | -2.7 °C | 8.3 °C | 44.96 mm |
| December | -8.6 °C | 0.9 °C | 34.04 mm |
| Annual | 3.3 °C | 15 °C | 898.38 mm |
| 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 : -28.9°C to -26.1°C |
| Plant Hardiness Zone - 2012 | Zone 5a : -28.9°C to -26.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |