Bethel, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.2 °C (low) to 15.6 °C (high). Annual precipitation averages 1309.4 Millimeters. Bethel is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.8 °C | 7.9 °C | 203.45 mm |
| February | 1.6 °C | 9.3 °C | 121.92 mm |
| March | 2.9 °C | 11.7 °C | 148.34 mm |
| April | 4.6 °C | 14.7 °C | 96.77 mm |
| May | 7.6 °C | 18.6 °C | 52.58 mm |
| June | 10.1 °C | 20.8 °C | 40.89 mm |
| July | 12 °C | 24.2 °C | 20.32 mm |
| August | 12.1 °C | 24.6 °C | 27.18 mm |
| September | 10 °C | 21.6 °C | 47.24 mm |
| October | 6.7 °C | 15.4 °C | 125.73 mm |
| November | 3.4 °C | 10.4 °C | 208.79 mm |
| December | 1.6 °C | 7.4 °C | 216.15 mm |
| Annual | 6.2 °C | 15.6 °C | 1309.36 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |