Rainier, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 6.5 °C (low) to 16.2 °C (high). Annual precipitation averages 1166.1 Millimeters. 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 | 2.1 °C | 8.1 °C | 168.15 mm |
| February | 1.7 °C | 10.1 °C | 108.46 mm |
| March | 3.2 °C | 12.7 °C | 128.52 mm |
| April | 4.9 °C | 15.1 °C | 107.19 mm |
| May | 7.9 °C | 18.8 °C | 60.2 mm |
| June | 10.3 °C | 21.1 °C | 45.21 mm |
| July | 12.4 °C | 24.7 °C | 11.18 mm |
| August | 12.4 °C | 25.4 °C | 17.02 mm |
| September | 10.1 °C | 22.9 °C | 57.15 mm |
| October | 6.8 °C | 16.7 °C | 109.22 mm |
| November | 3.9 °C | 11.2 °C | 167.64 mm |
| December | 1.8 °C | 7.7 °C | 186.18 mm |
| Annual | 6.5 °C | 16.2 °C | 1166.12 mm |
| 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 : -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 |