Atherton, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 49.1 °F (low) to 69.4 °F (high). Annual precipitation averages 18.4 Inches. Atherton is located in USDA Plant Hardiness Zone 9b. The growing season typically runs from the last frost around Jan. 21 - Jan. 31 through the first frost around Dec. 21 - Dec. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 42.1 °F | 58.5 °F | 3.71 in. |
| February | 43.8 °F | 61.2 °F | 3.81 in. |
| March | 45.7 °F | 64.2 °F | 2.68 in. |
| April | 47.3 °F | 67.8 °F | 1.3 in. |
| May | 50.8 °F | 71.8 °F | 0.47 in. |
| June | 53.6 °F | 76.6 °F | 0.13 in. |
| July | 56.1 °F | 78.4 °F | 0.0 in. |
| August | 56.2 °F | 78.5 °F | 0.03 in. |
| September | 55.2 °F | 78.3 °F | 0.07 in. |
| October | 51.4 °F | 73.8 °F | 0.73 in. |
| November | 45.7 °F | 64.5 °F | 1.7 in. |
| December | 41.8 °F | 58.6 °F | 3.72 in. |
| Annual | 49.1 °F | 69.4 °F | 18.35 in. |
| Average First Frost Date | Dec. 21 - Dec. 31 |
| Average Last Frost Date | Jan. 21 - Jan. 31 |
| 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 |