Upper Lake, California has a Hot-Summer Mediterranean Climate climate (Köppen classification: Csa). Average annual temperatures range from 41.8 °F (low) to 73 °F (high). Annual precipitation averages 35.8 Inches. 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 | 34.1 °F | 55.4 °F | 7.03 in. |
| February | 35.1 °F | 59.1 °F | 6.45 in. |
| March | 36.8 °F | 63.4 °F | 4.69 in. |
| April | 39.6 °F | 68.6 °F | 2.57 in. |
| May | 44.0 °F | 76.3 °F | 1.52 in. |
| June | 48.2 °F | 84.8 °F | 0.42 in. |
| July | 52.8 °F | 93.1 °F | 0.04 in. |
| August | 51.4 °F | 92.4 °F | 0.07 in. |
| September | 47.1 °F | 88.0 °F | 0.12 in. |
| October | 41.9 °F | 77.2 °F | 1.75 in. |
| November | 36.9 °F | 62.5 °F | 3.47 in. |
| December | 33.1 °F | 55.0 °F | 7.67 in. |
| Annual | 41.8 °F | 73 °F | 35.8 in. |
| 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 : 15°F to 20°F |
| Plant Hardiness Zone - 2012 | Zone 8b : 15°F to 20°F |
| Current Drought Conditions | Abnormally Dry |
| Köppen Climate Classification | Csa - Hot-Summer Mediterranean Climate |