Three Rivers, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 10.3 °C (low) to 25.6 °C (high). Annual precipitation averages 519.7 Millimeters. Three Rivers is located in USDA Plant Hardiness Zone 9b. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 21 - Nov. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 3.4 °C | 14.8 °C | 108.2 mm |
| February | 4.7 °C | 17.2 °C | 90.68 mm |
| March | 6.6 °C | 20.4 °C | 87.12 mm |
| April | 8.3 °C | 23.7 °C | 44.7 mm |
| May | 11.9 °C | 28.5 °C | 20.57 mm |
| June | 15.6 °C | 33.3 °C | 5.84 mm |
| July | 19.2 °C | 36.9 °C | 2.54 mm |
| August | 18.5 °C | 36.8 °C | 0.51 mm |
| September | 15.7 °C | 33.9 °C | 5.08 mm |
| October | 10.8 °C | 27.6 °C | 21.34 mm |
| November | 6.1 °C | 19.7 °C | 44.2 mm |
| December | 3.1 °C | 14.8 °C | 88.9 mm |
| Annual | 10.3 °C | 25.6 °C | 519.68 mm |
| Average First Frost Date | Nov. 21 - Nov. 30 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 20-30 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 |