Penryn, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 9.5 °C (low) to 23.4 °C (high). Annual precipitation averages 731.5 Millimeters. Penryn is located in USDA Plant Hardiness Zone 9b. The growing season typically runs from the last frost around Feb. 21 - Feb. 29 through the first frost around Dec. 1 - Dec. 10.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 3.8 °C | 13 °C | 125.73 mm |
| February | 4.8 °C | 15.4 °C | 120.4 mm |
| March | 6.4 °C | 18 °C | 105.41 mm |
| April | 7.6 °C | 21 °C | 59.44 mm |
| May | 10.8 °C | 25.9 °C | 44.96 mm |
| June | 14.1 °C | 30.9 °C | 9.65 mm |
| July | 16.5 °C | 34.8 °C | 0.25 mm |
| August | 16.2 °C | 34.2 °C | 0.76 mm |
| September | 14.2 °C | 31.3 °C | 4.83 mm |
| October | 10.3 °C | 25.4 °C | 37.59 mm |
| November | 6.2 °C | 17.8 °C | 81.03 mm |
| December | 3.4 °C | 12.9 °C | 141.48 mm |
| Annual | 9.5 °C | 23.4 °C | 731.53 mm |
| Average First Frost Date | Dec. 1 - Dec. 10 |
| Average Last Frost Date | Feb. 21 - Feb. 29 |
| Average Days With Frost | 10-20 Days |
| Plant Hardiness Zone | Zone 9b : -3.9°C to -1.1°C |
| Plant Hardiness Zone - 2012 | Zone 9b : -3.9°C to -1.1°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |