Rialto, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 11.4 °C (low) to 26.2 °C (high). Annual precipitation averages 379.8 Millimeters. Rialto is located in USDA Plant Hardiness Zone 10a. The growing season typically runs from the last frost around Feb. 1 - Feb. 10 through the first frost around Dec. 11 - Dec. 20.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 6.4 °C | 19.3 °C | 82.55 mm |
| February | 6.7 °C | 19.4 °C | 95.25 mm |
| March | 8.2 °C | 21.3 °C | 64.52 mm |
| April | 9.6 °C | 23.8 °C | 21.34 mm |
| May | 12.1 °C | 26.6 °C | 8.64 mm |
| June | 14.4 °C | 30.6 °C | 1.78 mm |
| July | 17.3 °C | 34.6 °C | 2.03 mm |
| August | 17.8 °C | 35.2 °C | 2.29 mm |
| September | 16.4 °C | 33.3 °C | 3.3 mm |
| October | 12.8 °C | 28 °C | 17.53 mm |
| November | 8.8 °C | 23.2 °C | 23.62 mm |
| December | 5.9 °C | 18.8 °C | 56.9 mm |
| Annual | 11.4 °C | 26.2 °C | 379.75 mm |
| Average First Frost Date | Dec. 11 - Dec. 20 |
| Average Last Frost Date | Feb. 1 - Feb. 10 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 10a : -1.1°C to 1.7°C |
| Plant Hardiness Zone - 2012 | Zone 10a : -1.1°C to 1.7°C |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |