Hayward, California has a Warm-Summer Mediterranean Climate climate (Köppen classification: Csb). Average annual temperatures range from 9.8 °C (low) to 20 °C (high). Annual precipitation averages 473 Millimeters. Hayward is located in USDA Plant Hardiness Zone 10a. The growing season typically runs from the last frost around Frost Rare through the first frost around Frost Rare.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 5.8 °C | 14.6 °C | 92.46 mm |
| February | 6.8 °C | 16.2 °C | 89.92 mm |
| March | 7.8 °C | 17.7 °C | 68.33 mm |
| April | 8.7 °C | 19 °C | 35.56 mm |
| May | 10.7 °C | 20.6 °C | 16.26 mm |
| June | 12.2 °C | 23 °C | 4.83 mm |
| July | 13.6 °C | 24.2 °C | 0.25 mm |
| August | 13.8 °C | 24.4 °C | 1.02 mm |
| September | 13.3 °C | 24.8 °C | 2.29 mm |
| October | 11.3 °C | 22.8 °C | 22.35 mm |
| November | 7.9 °C | 18.1 °C | 47.5 mm |
| December | 5.6 °C | 14.6 °C | 92.2 mm |
| Annual | 9.8 °C | 20 °C | 472.97 mm |
| Average First Frost Date | Frost Rare |
| Average Last Frost Date | Frost Rare |
| Average Days With Frost | Frost Rare |
| Plant Hardiness Zone | Zone 10a : -1.1°C to 1.7°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 |