Upper Lake, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 5.4 °C (low) to 22.8 °C (high). Annual precipitation averages 909.3 Millimeters. Upper Lake is located in USDA Plant Hardiness Zone 8b. The growing season typically runs from the last frost around Mar. 21 - Mar. 31 through the first frost around Nov. 21 - Nov. 30.
| Month | Avg. Low | Avg. High | Avg. Precip |
|---|---|---|---|
| January | 1.2 °C | 13 °C | 178.56 mm |
| February | 1.7 °C | 15.1 °C | 163.83 mm |
| March | 2.7 °C | 17.4 °C | 119.13 mm |
| April | 4.2 °C | 20.3 °C | 65.28 mm |
| May | 6.7 °C | 24.6 °C | 38.61 mm |
| June | 9 °C | 29.3 °C | 10.67 mm |
| July | 11.6 °C | 33.9 °C | 1.02 mm |
| August | 10.8 °C | 33.6 °C | 1.78 mm |
| September | 8.4 °C | 31.1 °C | 3.05 mm |
| October | 5.5 °C | 25.1 °C | 44.45 mm |
| November | 2.7 °C | 16.9 °C | 88.14 mm |
| December | 0.6 °C | 12.8 °C | 194.82 mm |
| Annual | 5.4 °C | 22.8 °C | 909.34 mm |
| Average First Frost Date | Nov. 21 - Nov. 30 |
| Average Last Frost Date | Mar. 21 - Mar. 31 |
| Average Days With Frost | 30-40 Days |
| Plant Hardiness Zone | Zone 8b : -9.4°C to -6.7°C |
| Plant Hardiness Zone - 2012 | Zone 8b : -9.4°C to -6.7°C |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |