Alamo, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 48 °F (low) to 71.9 °F (high). Annual precipitation averages 25.7 Inches. 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 | 40.1 °F | 56.9 °F | 5.18 in. |
| February | 41.5 °F | 60.9 °F | 5.14 in. |
| March | 43.7 °F | 65.1 °F | 3.72 in. |
| April | 45.9 °F | 69.7 °F | 1.77 in. |
| May | 49.9 °F | 74.2 °F | 0.89 in. |
| June | 53.4 °F | 81.4 °F | 0.14 in. |
| July | 56.0 °F | 86.0 °F | 0.02 in. |
| August | 56.2 °F | 86.0 °F | 0.04 in. |
| September | 54.8 °F | 84.5 °F | 0.09 in. |
| October | 50.7 °F | 75.8 °F | 1.11 in. |
| November | 43.6 °F | 64.8 °F | 2.31 in. |
| December | 39.6 °F | 56.9 °F | 5.26 in. |
| Annual | 48 °F | 71.9 °F | 25.67 in. |
| 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 : 25°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 9b : 25°F to 20°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |