Arlington, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 41.7 °F (low) to 60.2 °F (high). Annual precipitation averages 47.6 Inches. 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 | 33.8 °F | 46.3 °F | 5.68 in. |
| February | 33.5 °F | 49.2 °F | 4.22 in. |
| March | 35.9 °F | 53.1 °F | 4.97 in. |
| April | 39.9 °F | 58.9 °F | 4.17 in. |
| May | 44.9 °F | 65.4 °F | 3.11 in. |
| June | 49.2 °F | 69.2 °F | 2.48 in. |
| July | 51.7 °F | 75.7 °F | 1.15 in. |
| August | 51.6 °F | 76.7 °F | 1.22 in. |
| September | 47.8 °F | 71.5 °F | 2.45 in. |
| October | 41.5 °F | 60.4 °F | 4.92 in. |
| November | 36.7 °F | 51.0 °F | 6.78 in. |
| December | 33.4 °F | 45.3 °F | 6.47 in. |
| Annual | 41.7 °F | 60.2 °F | 47.62 in. |
| 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 : 10°F to 15°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |