Granite Falls, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 42.1 °F (low) to 59 °F (high). Annual precipitation averages 52.8 Inches. Granite Falls 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 | 33.2 °F | 45.0 °F | 6.95 in. |
| February | 33.4 °F | 48.1 °F | 4.95 in. |
| March | 35.8 °F | 52.4 °F | 5.62 in. |
| April | 39.8 °F | 57.5 °F | 4.42 in. |
| May | 45.4 °F | 64.2 °F | 3.1 in. |
| June | 49.7 °F | 68.1 °F | 3.04 in. |
| July | 53.3 °F | 74.7 °F | 1.22 in. |
| August | 53.3 °F | 75.6 °F | 1.18 in. |
| September | 48.9 °F | 69.8 °F | 2.79 in. |
| October | 42.5 °F | 58.9 °F | 5.57 in. |
| November | 36.8 °F | 49.7 °F | 7.41 in. |
| December | 33.1 °F | 44.0 °F | 6.51 in. |
| Annual | 42.1 °F | 59 °F | 52.76 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 |