Alger, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.9 °C (low) to 15.3 °C (high). Annual precipitation averages 1292.1 Millimeters. Alger is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 1 - Apr. 10 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.1 °C | 7.1 °C | 164.34 mm |
| February | 1.3 °C | 8.5 °C | 85.6 mm |
| March | 2.6 °C | 11.1 °C | 150.37 mm |
| April | 4.7 °C | 14.7 °C | 106.17 mm |
| May | 7.4 °C | 18.3 °C | 81.03 mm |
| June | 10 °C | 20.9 °C | 61.98 mm |
| July | 11.7 °C | 24.1 °C | 35.56 mm |
| August | 11.7 °C | 24.8 °C | 38.35 mm |
| September | 9.4 °C | 21.6 °C | 53.85 mm |
| October | 6.2 °C | 15.4 °C | 146.56 mm |
| November | 3.2 °C | 9.8 °C | 216.92 mm |
| December | 1 °C | 6.7 °C | 151.38 mm |
| Annual | 5.9 °C | 15.3 °C | 1292.11 mm |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 1 - Apr. 10 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |