Waterloo, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 8.9 °C (low) to 23.5 °C (high). Annual precipitation averages 426.7 Millimeters. Waterloo is located in USDA Plant Hardiness Zone 9b. The growing season typically runs from the last frost around Feb. 1 - Feb. 10 through the first frost around Dec. 1 - Dec. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 3.7 °C | 13.2 °C | 86.11 mm |
| February | 4.9 °C | 16.2 °C | 75.95 mm |
| March | 6.4 °C | 19.2 °C | 62.99 mm |
| April | 8 °C | 22.4 °C | 36.83 mm |
| May | 10.7 °C | 26.4 °C | 17.27 mm |
| June | 13.1 °C | 30.6 °C | 4.57 mm |
| July | 14.6 °C | 33.2 °C | 0.25 mm |
| August | 14.4 °C | 32.6 °C | 1.02 mm |
| September | 13.1 °C | 30.8 °C | 2.79 mm |
| October | 9.5 °C | 25.8 °C | 20.83 mm |
| November | 5.6 °C | 18.5 °C | 39.12 mm |
| December | 3.3 °C | 13.4 °C | 78.99 mm |
| Annual | 8.9 °C | 23.5 °C | 426.72 mm |
| Average First Frost Date | Dec. 1 - Dec. 10 |
| Average Last Frost Date | Feb. 1 - Feb. 10 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 9b : -3.9°C to -1.1°C |
| Plant Hardiness Zone - 2012 | Zone 9a : -6.7°C to -3.9°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |