Markham, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 44.9 °F (low) to 57.8 °F (high). Annual precipitation averages 80.3 Inches. Markham is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 39.0 °F | 48.3 °F | 12.62 in. |
| February | 38.1 °F | 50.4 °F | 7.54 in. |
| March | 39.6 °F | 52.6 °F | 9.3 in. |
| April | 42.2 °F | 55.9 °F | 6.31 in. |
| May | 46.5 °F | 60.2 °F | 3.37 in. |
| June | 50.4 °F | 63.6 °F | 2.49 in. |
| July | 53.2 °F | 67.0 °F | 1.06 in. |
| August | 53.2 °F | 68.2 °F | 1.57 in. |
| September | 51.0 °F | 67.2 °F | 2.83 in. |
| October | 46.0 °F | 60.2 °F | 8.17 in. |
| November | 41.4 °F | 52.6 °F | 12.44 in. |
| December | 38.2 °F | 47.9 °F | 12.55 in. |
| Annual | 44.9 °F | 57.8 °F | 80.25 in. |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 20-30 Days |
| Plant Hardiness Zone | Zone 9a : 20°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 9a : 20°F to 25°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |