Onalaska, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.1 °C (low) to 16.5 °C (high). Annual precipitation averages 1508.8 Millimeters. 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 | 0.9 °C | 7.7 °C | 206.5 mm |
| February | 0.8 °C | 9.9 °C | 143.76 mm |
| March | 1.9 °C | 12.4 °C | 162.31 mm |
| April | 3.6 °C | 15.6 °C | 130.05 mm |
| May | 6.6 °C | 19.7 °C | 86.11 mm |
| June | 8.8 °C | 22.3 °C | 68.83 mm |
| July | 10.8 °C | 26.3 °C | 24.64 mm |
| August | 10.8 °C | 26.9 °C | 27.94 mm |
| September | 8.4 °C | 23.4 °C | 58.93 mm |
| October | 5.2 °C | 16.6 °C | 142.75 mm |
| November | 2.5 °C | 10.5 °C | 231.65 mm |
| December | 0.7 °C | 7.1 °C | 225.3 mm |
| Annual | 5.1 °C | 16.5 °C | 1508.77 mm |
| 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 : -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 |