Swan, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 40.8 °F (low) to 60.6 °F (high). Annual precipitation averages 36.3 Inches. Swan 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 | 13.5 °F | 31.1 °F | 0.99 in. |
| February | 17.1 °F | 35.7 °F | 1.32 in. |
| March | 28.3 °F | 48.6 °F | 2.05 in. |
| April | 40.0 °F | 62.3 °F | 3.84 in. |
| May | 52.1 °F | 71.8 °F | 5.12 in. |
| June | 62.3 °F | 81.7 °F | 5.25 in. |
| July | 66.0 °F | 85.3 °F | 4.33 in. |
| August | 63.5 °F | 84.0 °F | 4.21 in. |
| September | 54.8 °F | 77.2 °F | 3.57 in. |
| October | 42.4 °F | 63.8 °F | 2.6 in. |
| November | 29.9 °F | 49.0 °F | 1.76 in. |
| December | 19.1 °F | 36.1 °F | 1.3 in. |
| Annual | 40.8 °F | 60.6 °F | 36.34 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 |