Millbrae, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 50.2 °F (low) to 66.2 °F (high). Annual precipitation averages 22.2 Inches. Millbrae is located in USDA Plant Hardiness Zone 10a.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 44.2 °F | 57.9 °F | 4.42 in. |
| February | 45.6 °F | 60.4 °F | 4.48 in. |
| March | 47.3 °F | 62.6 °F | 3.2 in. |
| April | 48.5 °F | 64.7 °F | 1.65 in. |
| May | 51.5 °F | 67.0 °F | 0.62 in. |
| June | 53.6 °F | 70.0 °F | 0.17 in. |
| July | 55.7 °F | 71.5 °F | 0.07 in. |
| August | 56.2 °F | 72.3 °F | 0.05 in. |
| September | 55.7 °F | 74.4 °F | 0.08 in. |
| October | 53.0 °F | 71.8 °F | 0.89 in. |
| November | 47.8 °F | 63.7 °F | 2.05 in. |
| December | 43.8 °F | 58.3 °F | 4.47 in. |
| Annual | 50.2 °F | 66.2 °F | 22.15 in. |
| Average First Frost Date | No Frost |
| Average Last Frost Date | |
| Average Days With Frost | Frost Free |
| Plant Hardiness Zone | Zone 10a : 30°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 10a : 30°F to 25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csb - Warm-Summer Mediterranean Climate |