Hartland, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 7.1 °C (low) to 18.9 °C (high). Annual precipitation averages 812 Millimeters. Hartland is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around May 1 - May 10 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.1 °C | 11.1 °C | 155.7 mm |
| February | 0.7 °C | 10.7 °C | 147.57 mm |
| March | 2.1 °C | 12.6 °C | 131.57 mm |
| April | 3.8 °C | 14.7 °C | 72.39 mm |
| May | 7.8 °C | 19.7 °C | 35.31 mm |
| June | 12.2 °C | 25.6 °C | 11.68 mm |
| July | 15.9 °C | 29.8 °C | 4.57 mm |
| August | 15.4 °C | 29.8 °C | 2.29 mm |
| September | 13.1 °C | 26.7 °C | 5.59 mm |
| October | 8 °C | 20.8 °C | 39.37 mm |
| November | 3.8 °C | 14.7 °C | 72.39 mm |
| December | 0.9 °C | 10.6 °C | 133.6 mm |
| Annual | 7.1 °C | 18.9 °C | 812.03 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | May 1 - May 10 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 9a : -6.7°C to -3.9°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |