Maltby, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.7 °C (low) to 15.1 °C (high). Annual precipitation averages 1188.5 Millimeters. Maltby 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 Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.2 °C | 7.8 °C | 155.19 mm |
| February | 2.2 °C | 9.2 °C | 114.3 mm |
| March | 3.4 °C | 11.3 °C | 122.94 mm |
| April | 5.2 °C | 13.8 °C | 101.35 mm |
| May | 8.2 °C | 17.7 °C | 70.87 mm |
| June | 10.3 °C | 20.1 °C | 64.77 mm |
| July | 12.4 °C | 23.6 °C | 26.16 mm |
| August | 12.7 °C | 23.9 °C | 27.69 mm |
| September | 10.7 °C | 20.7 °C | 58.42 mm |
| October | 7.3 °C | 14.8 °C | 113.28 mm |
| November | 3.9 °C | 10.3 °C | 174.24 mm |
| December | 2 °C | 7.4 °C | 159.26 mm |
| Annual | 6.7 °C | 15.1 °C | 1188.47 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 40-50 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 |