Simi Valley, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 10.8 °C (low) to 23.3 °C (high). Annual precipitation averages 396.2 Millimeters. 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 | 7.8 °C | 18.7 °C | 93.47 mm |
| February | 7.4 °C | 18.9 °C | 104.9 mm |
| March | 8.2 °C | 20.2 °C | 65.53 mm |
| April | 8.9 °C | 21.3 °C | 16.51 mm |
| May | 10.8 °C | 22.7 °C | 10.67 mm |
| June | 12.6 °C | 24.9 °C | 1.02 mm |
| July | 14.8 °C | 28.1 °C | 0.76 mm |
| August | 14.9 °C | 29.1 °C | 0 mm |
| September | 14.4 °C | 28.6 °C | 2.03 mm |
| October | 12.3 °C | 25.8 °C | 15.49 mm |
| November | 9.6 °C | 22.4 °C | 22.35 mm |
| December | 7.3 °C | 18.6 °C | 63.5 mm |
| Annual | 10.8 °C | 23.3 °C | 396.23 mm |
| 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 : -1.1°C to 1.7°C |
| Plant Hardiness Zone - 2012 | Zone 9b : -3.9°C to -1.1°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |