Jamestown, North Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from 30.5 °F (low) to 52 °F (high). Annual precipitation averages 20.8 Inches. Jamestown is located in USDA Plant Hardiness Zone 4a. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 0.1 °F | 18.6 °F | 0.49 in. |
| February | 3.8 °F | 23.2 °F | 0.43 in. |
| March | 16.2 °F | 35.8 °F | 0.76 in. |
| April | 29.6 °F | 52.7 °F | 1.2 in. |
| May | 42.7 °F | 66.8 °F | 3.1 in. |
| June | 54.0 °F | 76.3 °F | 3.59 in. |
| July | 58.3 °F | 81.4 °F | 3.64 in. |
| August | 55.3 °F | 80.3 °F | 2.28 in. |
| September | 46.1 °F | 71.3 °F | 2.35 in. |
| October | 32.9 °F | 55.2 °F | 1.74 in. |
| November | 19.3 °F | 38.0 °F | 0.63 in. |
| December | 7.4 °F | 24.1 °F | 0.61 in. |
| Annual | 30.5 °F | 52 °F | 20.82 in. |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 4a : -30°F to -25°F |
| Plant Hardiness Zone - 2012 | Zone 4a : -30°F to -25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |