Middletown, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 7.4 °C (low) to 23 °C (high). Annual precipitation averages 1038.6 Millimeters. Middletown is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 11 - Nov. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 2.4 °C | 13.8 °C | 226.57 mm |
| February | 3 °C | 15.3 °C | 195.58 mm |
| March | 4.2 °C | 17.6 °C | 125.73 mm |
| April | 5.7 °C | 20.2 °C | 61.98 mm |
| May | 8.5 °C | 24.7 °C | 38.61 mm |
| June | 11.7 °C | 29.8 °C | 4.83 mm |
| July | 13.6 °C | 34.2 °C | 0 mm |
| August | 13.3 °C | 33.6 °C | 0.76 mm |
| September | 11.3 °C | 30.7 °C | 2.29 mm |
| October | 8 °C | 24.5 °C | 48.26 mm |
| November | 4.2 °C | 17.8 °C | 99.82 mm |
| December | 2.3 °C | 13.6 °C | 234.19 mm |
| Annual | 7.4 °C | 23 °C | 1038.62 mm |
| Average First Frost Date | Nov. 11 - Nov. 20 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 20-30 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 9a : -6.7°C to -3.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |