Markham, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 7.2 °C (low) to 14.4 °C (high). Annual precipitation averages 2038.4 Millimeters. 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 | 3.9 °C | 9.1 °C | 320.55 mm |
| February | 3.4 °C | 10.2 °C | 191.52 mm |
| March | 4.2 °C | 11.4 °C | 236.22 mm |
| April | 5.7 °C | 13.3 °C | 160.27 mm |
| May | 8.1 °C | 15.7 °C | 85.6 mm |
| June | 10.2 °C | 17.6 °C | 63.25 mm |
| July | 11.8 °C | 19.4 °C | 26.92 mm |
| August | 11.8 °C | 20.1 °C | 39.88 mm |
| September | 10.6 °C | 19.6 °C | 71.88 mm |
| October | 7.8 °C | 15.7 °C | 207.52 mm |
| November | 5.2 °C | 11.4 °C | 315.98 mm |
| December | 3.4 °C | 8.8 °C | 318.77 mm |
| Annual | 7.2 °C | 14.4 °C | 2038.36 mm |
| 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 : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 9a : -6.7°C to -3.9°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |