Arlington, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.4 °C (low) to 15.7 °C (high). Annual precipitation averages 1209.6 Millimeters. Arlington is located in USDA Plant Hardiness Zone 8a. 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 | 1 °C | 7.9 °C | 144.27 mm |
| February | 0.8 °C | 9.6 °C | 107.19 mm |
| March | 2.2 °C | 11.7 °C | 126.24 mm |
| April | 4.4 °C | 14.9 °C | 105.92 mm |
| May | 7.2 °C | 18.6 °C | 78.99 mm |
| June | 9.6 °C | 20.7 °C | 62.99 mm |
| July | 10.9 °C | 24.3 °C | 29.21 mm |
| August | 10.9 °C | 24.8 °C | 30.99 mm |
| September | 8.8 °C | 21.9 °C | 62.23 mm |
| October | 5.3 °C | 15.8 °C | 124.97 mm |
| November | 2.6 °C | 10.6 °C | 172.21 mm |
| December | 0.8 °C | 7.4 °C | 164.34 mm |
| Annual | 5.4 °C | 15.7 °C | 1209.55 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 8a : -12.2°C to -9.4°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 |