Bolan, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 1.8 °C (low) to 12.5 °C (high). Annual precipitation averages 915.7 Millimeters. Bolan 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 | -14.2 °C | -4.9 °C | 25.15 mm |
| February | -12.1 °C | -2.4 °C | 26.92 mm |
| March | -5.3 °C | 4.5 °C | 49.28 mm |
| April | 1.4 °C | 13.1 °C | 96.77 mm |
| May | 8.2 °C | 19.9 °C | 126.49 mm |
| June | 14.3 °C | 25.4 °C | 135.64 mm |
| July | 16.1 °C | 27.1 °C | 118.36 mm |
| August | 14.6 °C | 25.8 °C | 104.65 mm |
| September | 9.8 °C | 22.4 °C | 87.88 mm |
| October | 2.8 °C | 14.8 °C | 67.06 mm |
| November | -3.9 °C | 5.9 °C | 43.69 mm |
| December | -10.3 °C | -1.7 °C | 33.78 mm |
| Annual | 1.8 °C | 12.5 °C | 915.67 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 150-180 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 | Abnormally Dry |
| Köppen Climate Classification | Dfa - Humid Continental Hot Summers With Year Around Precipitation |