Blairstown, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 3.5 °C (low) to 14.8 °C (high). Annual precipitation averages 937.8 Millimeters. Blairstown 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. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -11.5 °C | -2.2 °C | 28.7 mm |
| February | -9.5 °C | 0.4 °C | 32.51 mm |
| March | -3.2 °C | 7.8 °C | 53.59 mm |
| April | 2.9 °C | 15.7 °C | 94.23 mm |
| May | 9.8 °C | 21.8 °C | 119.89 mm |
| June | 15.6 °C | 27 °C | 135.89 mm |
| July | 17.4 °C | 28.8 °C | 107.19 mm |
| August | 15.9 °C | 27.8 °C | 107.7 mm |
| September | 11.1 °C | 24.4 °C | 91.95 mm |
| October | 4.4 °C | 17.1 °C | 72.39 mm |
| November | -2.3 °C | 8.4 °C | 53.59 mm |
| December | -8.1 °C | 0.9 °C | 40.13 mm |
| Annual | 3.5 °C | 14.8 °C | 937.76 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 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 |