Graham, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.5 °C (low) to 15.5 °C (high). Annual precipitation averages 1155.7 Millimeters. Graham 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 | 1.1 °C | 7.7 °C | 164.34 mm |
| February | 1 °C | 9.2 °C | 110.49 mm |
| March | 2.2 °C | 11.6 °C | 128.27 mm |
| April | 3.9 °C | 14.3 °C | 89.41 mm |
| May | 7 °C | 18.2 °C | 76.2 mm |
| June | 9.4 °C | 20.7 °C | 61.72 mm |
| July | 11.4 °C | 24.6 °C | 25.15 mm |
| August | 11.6 °C | 25.2 °C | 30.73 mm |
| September | 9.2 °C | 21.8 °C | 38.35 mm |
| October | 5.8 °C | 15.6 °C | 117.6 mm |
| November | 2.8 °C | 10.3 °C | 168.4 mm |
| December | 0.8 °C | 7.2 °C | 145.03 mm |
| Annual | 5.5 °C | 15.5 °C | 1155.69 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 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |