Bellevue, Washington has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 7.1 °C (low) to 15.9 °C (high). Annual precipitation averages 1071.9 Millimeters. Bellevue is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Mar. 1 - Mar. 10 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.3 °C | 8.4 °C | 143.51 mm |
| February | 2.4 °C | 9.9 °C | 103.12 mm |
| March | 3.7 °C | 12.1 °C | 110.74 mm |
| April | 5.6 °C | 14.9 °C | 86.87 mm |
| May | 8.6 °C | 18.7 °C | 57.15 mm |
| June | 11.1 °C | 21.1 °C | 53.59 mm |
| July | 13 °C | 24.7 °C | 20.83 mm |
| August | 13.1 °C | 25.1 °C | 26.67 mm |
| September | 11 °C | 21.8 °C | 46.74 mm |
| October | 7.6 °C | 15.8 °C | 108.2 mm |
| November | 4.3 °C | 10.9 °C | 159.77 mm |
| December | 2.2 °C | 7.9 °C | 154.69 mm |
| Annual | 7.1 °C | 15.9 °C | 1071.88 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 1 - Mar. 10 |
| Average Days With Frost | 20-30 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°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 |