McKenna, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 42.2 °F (low) to 61 °F (high). Annual precipitation averages 46.2 Inches. McKenna is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 34.4 °F | 46.7 °F | 6.63 in. |
| February | 34.2 °F | 49.6 °F | 4.49 in. |
| March | 36.3 °F | 53.9 °F | 5.15 in. |
| April | 39.3 °F | 59.0 °F | 3.72 in. |
| May | 44.7 °F | 66.0 °F | 2.33 in. |
| June | 49.3 °F | 70.5 °F | 1.87 in. |
| July | 52.8 °F | 77.4 °F | 0.69 in. |
| August | 52.8 °F | 78.4 °F | 1.01 in. |
| September | 48.6 °F | 72.6 °F | 1.69 in. |
| October | 42.6 °F | 61.1 °F | 4.59 in. |
| November | 37.3 °F | 51.3 °F | 7.41 in. |
| December | 34.0 °F | 45.7 °F | 6.61 in. |
| Annual | 42.2 °F | 61 °F | 46.19 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8b : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |