Graham, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 41.9 °F (low) to 59.9 °F (high). Annual precipitation averages 45.5 Inches. 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 | 34.0 °F | 45.9 °F | 6.47 in. |
| February | 33.8 °F | 48.5 °F | 4.35 in. |
| March | 36.0 °F | 52.8 °F | 5.05 in. |
| April | 39.1 °F | 57.7 °F | 3.52 in. |
| May | 44.6 °F | 64.8 °F | 3.0 in. |
| June | 48.9 °F | 69.2 °F | 2.43 in. |
| July | 52.5 °F | 76.3 °F | 0.99 in. |
| August | 52.8 °F | 77.3 °F | 1.21 in. |
| September | 48.6 °F | 71.2 °F | 1.51 in. |
| October | 42.4 °F | 60.0 °F | 4.63 in. |
| November | 37.0 °F | 50.5 °F | 6.63 in. |
| December | 33.5 °F | 45.0 °F | 5.71 in. |
| Annual | 41.9 °F | 59.9 °F | 45.5 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 8b : 15°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |