Grand River, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 39.4 °F (low) to 60.8 °F (high). Annual precipitation averages 38.1 Inches. Grand River is located in USDA Plant Hardiness Zone 5b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 13.1 °F | 32.1 °F | 0.93 in. |
| February | 16.9 °F | 36.8 °F | 1.36 in. |
| March | 27.8 °F | 49.7 °F | 2.19 in. |
| April | 38.3 °F | 61.8 °F | 4.05 in. |
| May | 49.9 °F | 71.6 °F | 5.43 in. |
| June | 60.0 °F | 81.1 °F | 5.16 in. |
| July | 64.4 °F | 85.5 °F | 4.41 in. |
| August | 61.8 °F | 83.9 °F | 4.28 in. |
| September | 52.6 °F | 76.7 °F | 3.91 in. |
| October | 40.6 °F | 64.4 °F | 2.85 in. |
| November | 28.6 °F | 49.5 °F | 2.09 in. |
| December | 18.7 °F | 37.0 °F | 1.44 in. |
| Annual | 39.4 °F | 60.8 °F | 38.1 in. |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 5b : -15°F to -10°F |
| Plant Hardiness Zone - 2012 | Zone 5b : -15°F to -10°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |