Harrah, Washington has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from 3.8 °C (low) to 17.9 °C (high). Annual precipitation averages 194.3 Millimeters. Harrah is located in USDA Plant Hardiness Zone 7a. 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 | -3.8 °C | 4 °C | 31.75 mm |
| February | -2.6 °C | 8.5 °C | 19.81 mm |
| March | 0.2 °C | 13.6 °C | 16 mm |
| April | 2.9 °C | 17.9 °C | 11.94 mm |
| May | 7.3 °C | 23.1 °C | 17.02 mm |
| June | 10.3 °C | 26.7 °C | 11.94 mm |
| July | 13.3 °C | 31.7 °C | 4.57 mm |
| August | 12.5 °C | 31.1 °C | 4.83 mm |
| September | 8.2 °C | 26.3 °C | 5.33 mm |
| October | 3 °C | 18.3 °C | 16 mm |
| November | -1.4 °C | 9.7 °C | 20.32 mm |
| December | -4.2 °C | 3.4 °C | 34.8 mm |
| Annual | 3.8 °C | 17.9 °C | 194.31 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 125-150 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 6b : -20.6°C to -17.8°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dsb - Humid Continental Climate - Dry Cool Summer |