Colusa, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 48.8 °F (low) to 74.8 °F (high). Annual precipitation averages 17.3 Inches. 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 | 38.7 °F | 55.6 °F | 3.58 in. |
| February | 41.2 °F | 61.0 °F | 3.26 in. |
| March | 43.5 °F | 66.5 °F | 2.17 in. |
| April | 46.1 °F | 72.7 °F | 1.13 in. |
| May | 52.9 °F | 80.7 °F | 0.82 in. |
| June | 58.5 °F | 88.0 °F | 0.2 in. |
| July | 60.9 °F | 92.9 °F | 0.02 in. |
| August | 59.0 °F | 92.1 °F | 0.08 in. |
| September | 55.7 °F | 88.8 °F | 0.13 in. |
| October | 49.3 °F | 79.3 °F | 0.85 in. |
| November | 42.0 °F | 64.8 °F | 1.9 in. |
| December | 38.2 °F | 55.6 °F | 3.18 in. |
| Annual | 48.8 °F | 74.8 °F | 17.32 in. |
| 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 : 25°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 9b : 25°F to 20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |