Onalaska, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 41.2 °F (low) to 61.8 °F (high). Annual precipitation averages 59.4 Inches. Onalaska is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 33.7 °F | 45.9 °F | 8.13 in. |
| February | 33.4 °F | 49.8 °F | 5.66 in. |
| March | 35.5 °F | 54.4 °F | 6.39 in. |
| April | 38.5 °F | 60.1 °F | 5.12 in. |
| May | 43.8 °F | 67.5 °F | 3.39 in. |
| June | 47.9 °F | 72.1 °F | 2.71 in. |
| July | 51.5 °F | 79.3 °F | 0.97 in. |
| August | 51.4 °F | 80.4 °F | 1.1 in. |
| September | 47.1 °F | 74.2 °F | 2.32 in. |
| October | 41.4 °F | 61.8 °F | 5.62 in. |
| November | 36.5 °F | 50.9 °F | 9.12 in. |
| December | 33.3 °F | 44.8 °F | 8.87 in. |
| Annual | 41.2 °F | 61.8 °F | 59.4 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8b : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8a : 10°F to 15°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |