Porter, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 5.3 °C (low) to 16.4 °C (high). Annual precipitation averages 1828.5 Millimeters. Porter is located in USDA Plant Hardiness Zone 8a. The growing season typically runs from the last frost around Apr. 21 - Apr. 30 through the first frost around Oct. 11 - Oct. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.4 °C | 8.3 °C | 284.99 mm |
| February | 1.1 °C | 10 °C | 181.36 mm |
| March | 2.1 °C | 12.3 °C | 202.69 mm |
| April | 3.6 °C | 15.7 °C | 138.68 mm |
| May | 6.6 °C | 19.5 °C | 79.76 mm |
| June | 9 °C | 21.8 °C | 57.91 mm |
| July | 11 °C | 25.2 °C | 19.3 mm |
| August | 10.9 °C | 25.7 °C | 34.04 mm |
| September | 8.7 °C | 23.1 °C | 67.56 mm |
| October | 5.4 °C | 17 °C | 178.31 mm |
| November | 2.7 °C | 10.9 °C | 297.43 mm |
| December | 1.1 °C | 7.7 °C | 286.51 mm |
| Annual | 5.3 °C | 16.4 °C | 1828.54 mm |
| Average First Frost Date | Oct. 11 - Oct. 20 |
| Average Last Frost Date | Apr. 21 - Apr. 30 |
| Average Days With Frost | 50-75 Days |
| Plant Hardiness Zone | Zone 8a : -12.2°C to -9.4°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 |