Yelm, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.5 °C (low) to 16.1 °C (high). Annual precipitation averages 1227.3 Millimeters. Yelm 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 Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.2 °C | 8.1 °C | 173.74 mm |
| February | 1.1 °C | 9.7 °C | 118.36 mm |
| March | 2.3 °C | 12.1 °C | 134.37 mm |
| April | 3.9 °C | 14.9 °C | 99.82 mm |
| May | 6.9 °C | 18.9 °C | 58.93 mm |
| June | 9.4 °C | 21.4 °C | 48.01 mm |
| July | 11.3 °C | 25.2 °C | 17.02 mm |
| August | 11.4 °C | 25.7 °C | 25.65 mm |
| September | 9.1 °C | 22.4 °C | 47.5 mm |
| October | 5.8 °C | 16 °C | 117.6 mm |
| November | 2.8 °C | 10.7 °C | 202.44 mm |
| December | 1.1 °C | 7.5 °C | 183.9 mm |
| Annual | 5.5 °C | 16.1 °C | 1227.34 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| 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 | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |