Lake Ketchum, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.9 °C (low) to 14.9 °C (high). Annual precipitation averages 880.1 Millimeters. Lake Ketchum is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.4 °C | 7.8 °C | 106.93 mm |
| February | 1.3 °C | 9.1 °C | 76.71 mm |
| March | 2.7 °C | 11.3 °C | 96.01 mm |
| April | 4.8 °C | 13.9 °C | 73.41 mm |
| May | 7.5 °C | 17.4 °C | 62.23 mm |
| June | 9.8 °C | 19.8 °C | 41.15 mm |
| July | 11.5 °C | 23.2 °C | 26.42 mm |
| August | 11.6 °C | 23.7 °C | 28.19 mm |
| September | 9.6 °C | 20.6 °C | 48.51 mm |
| October | 6.1 °C | 14.9 °C | 81.53 mm |
| November | 3.2 °C | 10.2 °C | 128.52 mm |
| December | 1.3 °C | 7.3 °C | 110.49 mm |
| Annual | 5.9 °C | 14.9 °C | 880.1 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |