Frost Dates for 94019 — Half Moon Bay, California

In the 82% of winters that bring a 32°F night, half of springs at Half Moon Bay, CA see their last 32°F night by February 6; only one in ten is past it by December 17, and one in ten still has one after March 25. Counting the winters with no freeze at all, the risk of a 32°F night after March 25 is under 8% and after February 6 41%. The 47 days between the even-odds date and the one-in-ten date is wider than at 96% 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 December 17 in half of years, as early as November 25 one year in ten, and holds off past February 13 one year in ten. A hard freeze of 28°F is less common: it came in 19% of winters. The freeze-free season lasts 328 days in a typical year, longer than at 79% of the 219 California stations; it reaches 365 days one year in ten and falls short of 266 one year in ten. On average 5 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 56 days longer, to about April 3, and return around November 20. A 24°F night is unusual: 2% of winters had one.

August is the warmest month at Half Moon Bay, CA, averaging 66°F by day and 54°F at night; December is the coldest at 59°F and 43°F. From April to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 31% of years and March still brings one in 17% of years.

Warmth for growing adds up to 1,952 growing degree days a year (base 50°F), fewer than at 94% of the 283 California stations. 36% of them (693) have built up by the end of June, and August adds the most, 302. Precipitation totals 26.1 inches a year, most in December (5.2") and least in July (0.1"); May to September bring 7% of it.

The nearest other station, Pacifica 4 SSE, CA, 8 miles north of Half Moon Bay and 448 feet higher, has a 32°F night in 20% of winters against 82% here, and a coolest-month low 2°F warmer (45°F).

Measurable snow is rare here: only 0 of 19 winters from 1991 to 2020 recorded 0.1 inch or more at Half Moon Bay, CA, 0.2 miles away, so there is no typical first-snow date to plan around.

ZIP 94019 is under a mile from Half Moon Bay, CA, which stands at 27 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 94019 in zone 10a, the band where the coldest night of the year averaged 30 to 35°F (-1.1 to 1.7°C) over 1991–2020; a zone describes winter lows, not frost dates.