Jamestown, North Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -0.9 °C (low) to 11.1 °C (high). Annual precipitation averages 528.8 Millimeters. 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 | -17.7 °C | -7.4 °C | 12.45 mm |
| February | -15.7 °C | -4.9 °C | 10.92 mm |
| March | -8.8 °C | 2.1 °C | 19.3 mm |
| April | -1.3 °C | 11.5 °C | 30.48 mm |
| May | 5.9 °C | 19.3 °C | 78.74 mm |
| June | 12.2 °C | 24.6 °C | 91.19 mm |
| July | 14.6 °C | 27.4 °C | 92.46 mm |
| August | 12.9 °C | 26.8 °C | 57.91 mm |
| September | 7.8 °C | 21.8 °C | 59.69 mm |
| October | 0.5 °C | 12.9 °C | 44.2 mm |
| November | -7.1 °C | 3.3 °C | 16 mm |
| December | -13.7 °C | -4.4 °C | 15.49 mm |
| Annual | -0.9 °C | 11.1 °C | 528.83 mm |
| 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 : -34.4°C to -31.7°C |
| Plant Hardiness Zone - 2012 | Zone 4a : -34.4°C to -31.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |