Granite Falls, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.6 °C (low) to 15 °C (high). Annual precipitation averages 1340.1 Millimeters. 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 | 0.7 °C | 7.2 °C | 176.53 mm |
| February | 0.8 °C | 8.9 °C | 125.73 mm |
| March | 2.1 °C | 11.3 °C | 142.75 mm |
| April | 4.3 °C | 14.2 °C | 112.27 mm |
| May | 7.4 °C | 17.9 °C | 78.74 mm |
| June | 9.8 °C | 20.1 °C | 77.22 mm |
| July | 11.8 °C | 23.7 °C | 30.99 mm |
| August | 11.8 °C | 24.2 °C | 29.97 mm |
| September | 9.4 °C | 21 °C | 70.87 mm |
| October | 5.8 °C | 14.9 °C | 141.48 mm |
| November | 2.7 °C | 9.8 °C | 188.21 mm |
| December | 0.6 °C | 6.7 °C | 165.35 mm |
| Annual | 5.6 °C | 15 °C | 1340.11 mm |
| 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 : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |