Cohasset, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 8 °C (low) to 20.7 °C (high). Annual precipitation averages 1438.1 Millimeters. Cohasset is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Jan. 21 - Jan. 31 through the first frost around Jan. 11 - Jan. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.2 °C | 11.6 °C | 278.38 mm |
| February | 2.6 °C | 12.6 °C | 236.73 mm |
| March | 3.8 °C | 14.7 °C | 203.45 mm |
| April | 5.1 °C | 17.7 °C | 117.86 mm |
| May | 8.7 °C | 22.4 °C | 72.39 mm |
| June | 12.7 °C | 27.9 °C | 25.65 mm |
| July | 16 °C | 32.4 °C | 1.52 mm |
| August | 15.4 °C | 32.1 °C | 4.06 mm |
| September | 13.6 °C | 29.3 °C | 10.92 mm |
| October | 9.3 °C | 22.7 °C | 72.39 mm |
| November | 4.6 °C | 14.8 °C | 138.94 mm |
| December | 1.8 °C | 10.6 °C | 275.84 mm |
| Annual | 8 °C | 20.7 °C | 1438.13 mm |
| Average First Frost Date | Jan. 11 - Jan. 20 |
| Average Last Frost Date | Jan. 21 - Jan. 31 |
| Average Days With Frost | 10-20 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 | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |