Keizer, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 43.3 °F (low) to 63.5 °F (high). Annual precipitation averages 41.1 Inches. Keizer is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Nov. 1 - Nov. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 35.6 °F | 47.4 °F | 5.89 in. |
| February | 35.7 °F | 51.1 °F | 4.48 in. |
| March | 37.8 °F | 55.8 °F | 4.83 in. |
| April | 40.7 °F | 60.5 °F | 3.43 in. |
| May | 45.9 °F | 67.8 °F | 2.28 in. |
| June | 50.0 °F | 73.4 °F | 1.52 in. |
| July | 53.6 °F | 82.2 °F | 0.37 in. |
| August | 53.4 °F | 82.7 °F | 0.37 in. |
| September | 49.8 °F | 76.7 °F | 1.51 in. |
| October | 43.7 °F | 64.2 °F | 3.44 in. |
| November | 38.8 °F | 53.0 °F | 5.91 in. |
| December | 35.0 °F | 46.6 °F | 7.07 in. |
| Annual | 43.3 °F | 63.5 °F | 41.1 in. |
| Average First Frost Date | Nov. 1 - Nov. 10 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 40-50 Days |
| Plant Hardiness Zone | Zone 8b : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Moderate Drought |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |