Alsea, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.3 °C (low) to 16.5 °C (high). Annual precipitation averages 1761.8 Millimeters. Alsea 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. 21 - Nov. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.5 °C | 8 °C | 273.05 mm |
| February | 1.5 °C | 10 °C | 217.17 mm |
| March | 2.5 °C | 12.4 °C | 220.73 mm |
| April | 3.8 °C | 15.6 °C | 131.32 mm |
| May | 6.4 °C | 19.1 °C | 84.84 mm |
| June | 8.4 °C | 21.8 °C | 48.51 mm |
| July | 10.2 °C | 26.3 °C | 10.67 mm |
| August | 10.3 °C | 26.4 °C | 12.7 mm |
| September | 8.7 °C | 23.7 °C | 54.86 mm |
| October | 5.9 °C | 16.8 °C | 129.79 mm |
| November | 3.3 °C | 10.9 °C | 266.45 mm |
| December | 1.3 °C | 7.4 °C | 311.66 mm |
| Annual | 5.3 °C | 16.5 °C | 1761.75 mm |
| Average First Frost Date | Nov. 21 - Nov. 30 |
| 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 | Moderate Drought |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |