Frost Dates for 95485 — Upper Lake, California

Half of springs at Ukiah Municipal Airport, CA see their last 32°F night by March 5; only one in ten is past it by January 29, and one in ten still has one after April 7. Planting tender crops after March 19 leaves a 30% risk of a frost on them, after March 29 20%, and after April 7 10%. The 33 days between the even-odds date and the one-in-ten date is wider than at 61% of the 220 California stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.

In fall the first 32°F night comes by November 21 in half of years, as early as November 2 one year in ten, and holds off past December 9 one year in ten. A hard freeze of 28°F follows 14 days later, around December 5; in spring the one-in-ten date for 28°F is February 28, 38 days before the 32°F one. The freeze-free season lasts 259 days in a typical year, shorter than at 63% of the 219 California stations; it reaches 300 days one year in ten and falls short of 221 one year in ten. On average 36 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 38 days longer, to about April 12, and return around November 2. Nights of 24°F, cold enough to damage hardier plants, come in 59% of winters and 16°F in 2%.

July is the warmest month at Ukiah Municipal Airport, CA, averaging 94°F by day and 56°F at night; December is the coldest at 57°F and 36°F. A freezing night is all but certain in December (a 90% chance or more). From May to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 75% of years and March still brings one in 50% of years and April still brings one in 16% of years.

Warmth for growing adds up to 3,991 growing degree days a year (base 50°F), fewer than at 60% of the 283 California stations. 34% of them (1,368) have built up by the end of June, and July adds the most, 777. Precipitation totals 34.9 inches a year, most in December (6.9") and least in July (0.0"); May to September bring 5% of it.

The nearest other station, Ukiah, CA, 16 miles west of Upper Lake, has a last frost 14 days later (March 19), a first frost 1 day earlier (November 20), a season 14 days shorter.

Measurable snow is rare here: only 1 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Ukiah, CA, 16.5 miles away, so there is no typical first-snow date to plan around.

ZIP 95485 is 16 miles from Ukiah Municipal Airport, CA, which stands at 601 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 95453 (Lakeport). The 2023 USDA Plant Hardiness Zone Map lists ZIP 95485 in zone 9a, the band where the coldest night of the year averaged 20 to 25°F (-6.7 to -3.9°C) over 1991–2020; a zone describes winter lows, not frost dates.