Brier, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.7 °C (low) to 15.4 °C (high). Annual precipitation averages 1044.5 Millimeters. Brier is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Mar. 11 - Mar. 20 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.2 °C | 8.2 °C | 141.48 mm |
| February | 2.1 °C | 9.6 °C | 99.57 mm |
| March | 3.4 °C | 11.8 °C | 110.74 mm |
| April | 5.2 °C | 14.3 °C | 86.11 mm |
| May | 8.1 °C | 18.1 °C | 54.36 mm |
| June | 10.3 °C | 20.3 °C | 52.83 mm |
| July | 12.4 °C | 23.8 °C | 23.62 mm |
| August | 12.7 °C | 24.2 °C | 28.96 mm |
| September | 10.7 °C | 20.9 °C | 43.43 mm |
| October | 7.2 °C | 15.4 °C | 99.06 mm |
| November | 3.9 °C | 10.6 °C | 159 mm |
| December | 1.9 °C | 7.7 °C | 145.29 mm |
| Annual | 6.7 °C | 15.4 °C | 1044.45 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 11 - Mar. 20 |
| 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 |