La Grande, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.2 °C (low) to 15.7 °C (high). Annual precipitation averages 1024.9 Millimeters. La Grande is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 0.8 °C | 7.3 °C | 134.11 mm |
| February | 0.8 °C | 8.6 °C | 84.58 mm |
| March | 1.9 °C | 11 °C | 125.22 mm |
| April | 3.5 °C | 14.7 °C | 99.57 mm |
| May | 6.6 °C | 19.1 °C | 72.9 mm |
| June | 8.9 °C | 21.7 °C | 54.86 mm |
| July | 11.1 °C | 25.7 °C | 19.81 mm |
| August | 11.3 °C | 26.3 °C | 25.91 mm |
| September | 9.1 °C | 22.3 °C | 41.4 mm |
| October | 5.6 °C | 15.5 °C | 95.76 mm |
| November | 2.4 °C | 9.6 °C | 140.97 mm |
| December | 0.5 °C | 6.7 °C | 129.79 mm |
| Annual | 5.2 °C | 15.7 °C | 1024.88 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| 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 |