Johnstonville, California has a Humid Continental Climate - Dry Cool Summer climate (Köppen classification: Dsb). Average annual temperatures range from 1.8 °C (low) to 18.2 °C (high). Annual precipitation averages 421.1 Millimeters. Johnstonville is located in USDA Plant Hardiness Zone 7a. The growing season typically runs from the last frost around May 11 - May 20 through the first frost around Oct. 1 - Oct. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | -5.1 °C | 6.3 °C | 86.61 mm |
| February | -3.8 °C | 8.7 °C | 64.01 mm |
| March | -1.2 °C | 12.5 °C | 51.56 mm |
| April | 0.4 °C | 15.9 °C | 21.34 mm |
| May | 4 °C | 21.2 °C | 24.38 mm |
| June | 7.3 °C | 26.8 °C | 14.99 mm |
| July | 10.7 °C | 31.9 °C | 5.33 mm |
| August | 9.8 °C | 31.2 °C | 4.06 mm |
| September | 6.2 °C | 27.2 °C | 6.6 mm |
| October | 1.6 °C | 19.6 °C | 27.69 mm |
| November | -2.7 °C | 11.4 °C | 35.31 mm |
| December | -5.6 °C | 5.9 °C | 79.25 mm |
| Annual | 1.8 °C | 18.2 °C | 421.13 mm |
| Average First Frost Date | Oct. 1 - Oct. 10 |
| Average Last Frost Date | May 11 - May 20 |
| Average Days With Frost | 150-180 Days |
| Plant Hardiness Zone | Zone 7a : -17.8°C to -15°C |
| Plant Hardiness Zone - 2012 | Zone 7a : -17.8°C to -15°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Dsb - Humid Continental Climate - Dry Cool Summer |