Perth, North Dakota has a Humid Continental Mild Summer, Wet All Year climate (Köppen classification: Dfb). Average annual temperatures range from -2.7 °C (low) to 8.8 °C (high). Annual precipitation averages 517.2 Millimeters. Perth is located in USDA Plant Hardiness Zone 3b. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Sep.11 - Sep. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -19.9 °C | -9.7 °C | 15.75 mm |
| February | -18.1 °C | -7.3 °C | 16 mm |
| March | -10.9 °C | -0.7 °C | 22.1 mm |
| April | -2.8 °C | 9.3 °C | 24.38 mm |
| May | 4.3 °C | 17.3 °C | 70.36 mm |
| June | 10.6 °C | 22.3 °C | 95 mm |
| July | 12.8 °C | 25.1 °C | 82.55 mm |
| August | 11.4 °C | 25.1 °C | 66.55 mm |
| September | 6.2 °C | 19.8 °C | 48.01 mm |
| October | -0.9 °C | 10.8 °C | 37.08 mm |
| November | -9 °C | 0.7 °C | 20.07 mm |
| December | -16.3 °C | -7 °C | 19.3 mm |
| Annual | -2.7 °C | 8.8 °C | 517.15 mm |
| Average First Frost Date | Sep.11 - Sep. 20 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 3b : -37.2°C to -34.4°C |
| Plant Hardiness Zone - 2012 | Zone 3b : -37.2°C to -34.4°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Dfb - Humid Continental Mild Summer, Wet All Year |