Oak Glen, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 7.4 °C (low) to 20.4 °C (high). Annual precipitation averages 621.8 Millimeters. Oak Glen is located in USDA Plant Hardiness Zone 9a. The growing season typically runs from the last frost around Apr. 11 - Apr. 20 through the first frost around Oct. 21 - Oct. 31.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.7 °C | 12.8 °C | 127.76 mm |
| February | 1.5 °C | 12.8 °C | 158.5 mm |
| March | 2.8 °C | 15.3 °C | 105.92 mm |
| April | 4.2 °C | 17.6 °C | 42.67 mm |
| May | 7.3 °C | 21.6 °C | 19.3 mm |
| June | 11.6 °C | 26.4 °C | 4.32 mm |
| July | 16 °C | 29.9 °C | 6.6 mm |
| August | 16.1 °C | 30.1 °C | 3.81 mm |
| September | 13.4 °C | 27.7 °C | 11.43 mm |
| October | 8.7 °C | 21.9 °C | 20.57 mm |
| November | 4.6 °C | 16.8 °C | 38.1 mm |
| December | 1.4 °C | 12.4 °C | 82.8 mm |
| Annual | 7.4 °C | 20.4 °C | 621.78 mm |
| Average First Frost Date | Oct. 21 - Oct. 31 |
| Average Last Frost Date | Apr. 11 - Apr. 20 |
| Average Days With Frost | 75-100 Days |
| Plant Hardiness Zone | Zone 9a : -6.7°C to -3.9°C |
| Plant Hardiness Zone - 2012 | Zone 8a : -12.2°C to -9.4°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |