Atherton, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 9.5 °C (low) to 20.8 °C (high). Annual precipitation averages 466.1 Millimeters. 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 | 5.6 °C | 14.7 °C | 94.23 mm |
| February | 6.6 °C | 16.2 °C | 96.77 mm |
| March | 7.6 °C | 17.9 °C | 68.07 mm |
| April | 8.5 °C | 19.9 °C | 33.02 mm |
| May | 10.4 °C | 22.1 °C | 11.94 mm |
| June | 12 °C | 24.8 °C | 3.3 mm |
| July | 13.4 °C | 25.8 °C | 0 mm |
| August | 13.4 °C | 25.8 °C | 0.76 mm |
| September | 12.9 °C | 25.7 °C | 1.78 mm |
| October | 10.8 °C | 23.2 °C | 18.54 mm |
| November | 7.6 °C | 18.1 °C | 43.18 mm |
| December | 5.4 °C | 14.8 °C | 94.49 mm |
| Annual | 9.5 °C | 20.8 °C | 466.08 mm |
| 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 : -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 |