Alamo, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 8.9 °C (low) to 22.1 °C (high). Annual precipitation averages 652 Millimeters. Alamo is located in USDA Plant Hardiness Zone 9b. The growing season typically runs from the last frost around Feb. 11 - Feb. 20 through the first frost around Dec. 21 - Dec. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 4.5 °C | 13.8 °C | 131.57 mm |
| February | 5.3 °C | 16.1 °C | 130.56 mm |
| March | 6.5 °C | 18.4 °C | 94.49 mm |
| April | 7.7 °C | 20.9 °C | 44.96 mm |
| May | 9.9 °C | 23.4 °C | 22.61 mm |
| June | 11.9 °C | 27.4 °C | 3.56 mm |
| July | 13.3 °C | 30 °C | 0.51 mm |
| August | 13.4 °C | 30 °C | 1.02 mm |
| September | 12.7 °C | 29.2 °C | 2.29 mm |
| October | 10.4 °C | 24.3 °C | 28.19 mm |
| November | 6.4 °C | 18.2 °C | 58.67 mm |
| December | 4.2 °C | 13.8 °C | 133.6 mm |
| Annual | 8.9 °C | 22.1 °C | 652.03 mm |
| Average First Frost Date | Dec. 21 - Dec. 31 |
| Average Last Frost Date | Feb. 11 - Feb. 20 |
| Average Days With Frost | Frost Rare |
| Plant Hardiness Zone | Zone 9b : -3.9°C to -1.1°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 |