Grand Junction, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 38 °F (low) to 59 °F (high). Annual precipitation averages 35.4 Inches. 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 | 10.3 °F | 28.3 °F | 0.91 in. |
| February | 14.6 °F | 33.1 °F | 1.16 in. |
| March | 26.0 °F | 46.4 °F | 2.01 in. |
| April | 37.1 °F | 60.9 °F | 3.75 in. |
| May | 49.4 °F | 71.5 °F | 4.98 in. |
| June | 59.8 °F | 80.8 °F | 5.27 in. |
| July | 63.4 °F | 84.4 °F | 4.25 in. |
| August | 60.8 °F | 82.2 °F | 4.11 in. |
| September | 51.8 °F | 76.4 °F | 3.21 in. |
| October | 39.4 °F | 63.5 °F | 2.61 in. |
| November | 27.2 °F | 47.0 °F | 1.77 in. |
| December | 16.5 °F | 33.7 °F | 1.34 in. |
| Annual | 38 °F | 59 °F | 35.37 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 | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |