Ontario, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 52.4 °F (low) to 78.3 °F (high). Annual precipitation averages 14.6 Inches. Ontario is located in USDA Plant Hardiness Zone 10a.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 43.9 °F | 67.3 °F | 3.3 in. |
| February | 44.6 °F | 67.6 °F | 3.87 in. |
| March | 46.9 °F | 70.7 °F | 2.33 in. |
| April | 49.4 °F | 74.5 °F | 0.69 in. |
| May | 53.6 °F | 78.3 °F | 0.38 in. |
| June | 57.5 °F | 84.7 °F | 0.1 in. |
| July | 62.2 °F | 91.3 °F | 0.05 in. |
| August | 63.0 °F | 93.1 °F | 0.02 in. |
| September | 61.1 °F | 90.1 °F | 0.11 in. |
| October | 55.2 °F | 81.9 °F | 0.62 in. |
| November | 47.9 °F | 73.9 °F | 0.81 in. |
| December | 43.2 °F | 66.4 °F | 2.28 in. |
| Annual | 52.4 °F | 78.3 °F | 14.56 in. |
| Average First Frost Date | No Frost |
| Average Last Frost Date | |
| Average Days With Frost | Frost Free |
| Plant Hardiness Zone | Zone 10a : 30°F to 25°F |
| Plant Hardiness Zone - 2012 | Zone 10a : 30°F to 25°F |
| Current Drought Conditions | Normal |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |