Martha Lake, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.8 °C (low) to 14.8 °C (high). Annual precipitation averages 1124.2 Millimeters. Martha Lake is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.2 °C | 7.8 °C | 145.54 mm |
| February | 2.2 °C | 9.1 °C | 111.25 mm |
| March | 3.6 °C | 11.3 °C | 120.65 mm |
| April | 5.3 °C | 13.7 °C | 93.22 mm |
| May | 8.2 °C | 17.4 °C | 65.02 mm |
| June | 10.3 °C | 19.6 °C | 52.58 mm |
| July | 12.3 °C | 22.8 °C | 23.88 mm |
| August | 12.7 °C | 23.3 °C | 27.69 mm |
| September | 10.8 °C | 20.3 °C | 52.58 mm |
| October | 7.5 °C | 14.7 °C | 105.41 mm |
| November | 4 °C | 10.2 °C | 174.24 mm |
| December | 2.1 °C | 7.4 °C | 152.15 mm |
| Annual | 6.8 °C | 14.8 °C | 1124.21 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 30-40 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°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 |