Grand Ronde, Oregon has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.9 °C (low) to 17.1 °C (high). Annual precipitation averages 1599.9 Millimeters. Grand Ronde 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. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.8 °C | 8.2 °C | 258.06 mm |
| February | 1.9 °C | 10.3 °C | 189.23 mm |
| March | 2.9 °C | 12.7 °C | 171.96 mm |
| April | 4.3 °C | 15.8 °C | 128.78 mm |
| May | 7 °C | 19.8 °C | 68.83 mm |
| June | 9.2 °C | 22.6 °C | 43.94 mm |
| July | 11.1 °C | 26.8 °C | 7.11 mm |
| August | 11.2 °C | 27.4 °C | 10.67 mm |
| September | 9.6 °C | 24.7 °C | 44.45 mm |
| October | 6.5 °C | 17.7 °C | 129.03 mm |
| November | 3.6 °C | 11.3 °C | 245.11 mm |
| December | 1.5 °C | 7.7 °C | 302.77 mm |
| Annual | 5.9 °C | 17.1 °C | 1599.94 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| 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 | Abnormally Dry |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |