Simi Valley, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 51.4 °F (low) to 73.9 °F (high). Annual precipitation averages 15.6 Inches. Simi Valley is located in USDA Plant Hardiness Zone 10a. The growing season typically runs from the last frost around Jan. 21 - Jan. 31 through the first frost around Jan. 1 - Jan. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 46.0 °F | 65.7 °F | 3.68 in. |
| February | 45.4 °F | 66.1 °F | 4.13 in. |
| March | 46.7 °F | 68.4 °F | 2.58 in. |
| April | 48.1 °F | 70.3 °F | 0.65 in. |
| May | 51.5 °F | 72.9 °F | 0.42 in. |
| June | 54.6 °F | 76.8 °F | 0.04 in. |
| July | 58.6 °F | 82.5 °F | 0.03 in. |
| August | 58.9 °F | 84.3 °F | 0.0 in. |
| September | 57.9 °F | 83.4 °F | 0.08 in. |
| October | 54.2 °F | 78.4 °F | 0.61 in. |
| November | 49.3 °F | 72.4 °F | 0.88 in. |
| December | 45.2 °F | 65.5 °F | 2.5 in. |
| Annual | 51.4 °F | 73.9 °F | 15.6 in. |
| Average First Frost Date | Jan. 1 - Jan. 10 |
| Average Last Frost Date | Jan. 21 - Jan. 31 |
| Average Days With Frost | Frost Rare |
| Plant Hardiness Zone | Zone 10a : 30°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 9b : 25°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |