Colusa, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 9.4 °C (low) to 23.8 °C (high). Annual precipitation averages 439.9 Millimeters. Colusa is located in USDA Plant Hardiness Zone 9b. The growing season typically runs from the last frost around Feb. 1 - Feb. 10 through the first frost around Nov. 21 - Nov. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 3.7 °C | 13.1 °C | 90.93 mm |
| February | 5.1 °C | 16.1 °C | 82.8 mm |
| March | 6.4 °C | 19.2 °C | 55.12 mm |
| April | 7.8 °C | 22.6 °C | 28.7 mm |
| May | 11.6 °C | 27.1 °C | 20.83 mm |
| June | 14.7 °C | 31.1 °C | 5.08 mm |
| July | 16.1 °C | 33.8 °C | 0.51 mm |
| August | 15 °C | 33.4 °C | 2.03 mm |
| September | 13.2 °C | 31.6 °C | 3.3 mm |
| October | 9.6 °C | 26.3 °C | 21.59 mm |
| November | 5.6 °C | 18.2 °C | 48.26 mm |
| December | 3.4 °C | 13.1 °C | 80.77 mm |
| Annual | 9.4 °C | 23.8 °C | 439.92 mm |
| Average First Frost Date | Nov. 21 - Nov. 30 |
| Average Last Frost Date | Feb. 1 - Feb. 10 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 9b : -3.9°C to -1.1°C |
| Plant Hardiness Zone - 2012 | Zone 9b : -3.9°C to -1.1°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |