Middletown, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 45.3 °F (low) to 73.4 °F (high). Annual precipitation averages 40.9 Inches. 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 | 36.4 °F | 56.8 °F | 8.92 in. |
| February | 37.4 °F | 59.6 °F | 7.7 in. |
| March | 39.6 °F | 63.6 °F | 4.95 in. |
| April | 42.3 °F | 68.3 °F | 2.44 in. |
| May | 47.3 °F | 76.4 °F | 1.52 in. |
| June | 53.1 °F | 85.7 °F | 0.19 in. |
| July | 56.5 °F | 93.6 °F | 0.0 in. |
| August | 55.9 °F | 92.5 °F | 0.03 in. |
| September | 52.3 °F | 87.2 °F | 0.09 in. |
| October | 46.4 °F | 76.1 °F | 1.9 in. |
| November | 39.6 °F | 64.0 °F | 3.93 in. |
| December | 36.2 °F | 56.4 °F | 9.22 in. |
| Annual | 45.3 °F | 73.4 °F | 40.89 in. |
| 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 : 20°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 9a : 20°F to 25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |