Yelm, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 41.9 °F (low) to 60.9 °F (high). Annual precipitation averages 48.3 Inches. 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 | 34.2 °F | 46.5 °F | 6.84 in. |
| February | 34.0 °F | 49.5 °F | 4.66 in. |
| March | 36.1 °F | 53.8 °F | 5.29 in. |
| April | 39.0 °F | 58.9 °F | 3.93 in. |
| May | 44.4 °F | 66.0 °F | 2.32 in. |
| June | 48.9 °F | 70.5 °F | 1.89 in. |
| July | 52.4 °F | 77.4 °F | 0.67 in. |
| August | 52.5 °F | 78.2 °F | 1.01 in. |
| September | 48.3 °F | 72.4 °F | 1.87 in. |
| October | 42.4 °F | 60.8 °F | 4.63 in. |
| November | 37.1 °F | 51.2 °F | 7.97 in. |
| December | 33.9 °F | 45.5 °F | 7.24 in. |
| Annual | 41.9 °F | 60.9 °F | 48.32 in. |
| 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 : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |