La Grande, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 41.4 °F (low) to 60.3 °F (high). Annual precipitation averages 40.4 Inches. 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 | 33.5 °F | 45.1 °F | 5.28 in. |
| February | 33.4 °F | 47.4 °F | 3.33 in. |
| March | 35.4 °F | 51.8 °F | 4.93 in. |
| April | 38.3 °F | 58.4 °F | 3.92 in. |
| May | 43.9 °F | 66.4 °F | 2.87 in. |
| June | 48.0 °F | 71.0 °F | 2.16 in. |
| July | 52.0 °F | 78.3 °F | 0.78 in. |
| August | 52.4 °F | 79.4 °F | 1.02 in. |
| September | 48.4 °F | 72.2 °F | 1.63 in. |
| October | 42.0 °F | 59.9 °F | 3.77 in. |
| November | 36.4 °F | 49.2 °F | 5.55 in. |
| December | 32.9 °F | 44.0 °F | 5.11 in. |
| Annual | 41.4 °F | 60.3 °F | 40.35 in. |
| 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 : 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 |