Williamsburg, Iowa has a Humid Continental Hot Summers With Year Around Precipitation climate (Köppen classification: Dfa). Average annual temperatures range from 38.9 °F (low) to 59.4 °F (high). Annual precipitation averages 37 Inches. Williamsburg 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 | 11.9 °F | 29.0 °F | 1.16 in. |
| February | 15.7 °F | 33.8 °F | 1.39 in. |
| March | 26.8 °F | 46.9 °F | 2.18 in. |
| April | 37.7 °F | 60.7 °F | 3.61 in. |
| May | 50.1 °F | 71.7 °F | 4.89 in. |
| June | 60.5 °F | 81.1 °F | 4.89 in. |
| July | 63.8 °F | 84.4 °F | 4.29 in. |
| August | 61.1 °F | 82.7 °F | 4.38 in. |
| September | 52.1 °F | 76.5 °F | 3.55 in. |
| October | 40.2 °F | 63.4 °F | 2.84 in. |
| November | 28.3 °F | 47.7 °F | 2.12 in. |
| December | 18.0 °F | 34.5 °F | 1.66 in. |
| Annual | 38.9 °F | 59.4 °F | 36.96 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 |