Rainier, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 43.6 °F (low) to 61.2 °F (high). Annual precipitation averages 45.9 Inches. Rainier is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 35.7 °F | 46.6 °F | 6.62 in. |
| February | 35.1 °F | 50.2 °F | 4.27 in. |
| March | 37.8 °F | 54.8 °F | 5.06 in. |
| April | 40.9 °F | 59.1 °F | 4.22 in. |
| May | 46.3 °F | 65.9 °F | 2.37 in. |
| June | 50.5 °F | 70.0 °F | 1.78 in. |
| July | 54.3 °F | 76.5 °F | 0.44 in. |
| August | 54.3 °F | 77.7 °F | 0.67 in. |
| September | 50.2 °F | 73.3 °F | 2.25 in. |
| October | 44.2 °F | 62.0 °F | 4.3 in. |
| November | 39.0 °F | 52.1 °F | 6.6 in. |
| December | 35.3 °F | 45.8 °F | 7.33 in. |
| Annual | 43.6 °F | 61.2 °F | 45.91 in. |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 50-75 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 | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |