Frost Dates for 93453 — Santa Margarita, California

Half of springs at Twitchell Dam, CA see their last 32°F night by February 4; only one in ten is past it by December 27, and one in ten still has one after March 31. Planting tender crops after February 27 leaves a 30% risk of a frost on them, after March 9 20%, and after March 31 10%. The 55 days between the even-odds date and the one-in-ten date is the widest of the 221 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 4 in half of years, as early as November 14 one year in ten, and holds off past December 28 one year in ten. A hard freeze of 28°F follows 13 days later, around December 17; in spring the one-in-ten date for 28°F is February 3, 56 days before the 32°F one. The freeze-free season lasts 301 days in a typical year, longer than at 64% of the 220 California stations; it reaches 343 days one year in ten and falls short of 244 one year in ten. On average 15 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 55 days longer, to about March 31, and return around November 16. A 24°F night is unusual: 13% of winters had one.

August is the warmest month at Twitchell Dam, CA, averaging 78°F by day and 54°F at night; December is the coldest at 61°F and 39°F. From April to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 39% of years and March still brings one in 19% of years.

Warmth for growing adds up to 3,267 growing degree days a year (base 50°F), fewer than at 78% of the 284 California stations. 37% of them (1,215) have built up by the end of June, and August adds the most, 488. Precipitation totals 18.3 inches a year, most in January (4.0") and least in July (0.0"); May to September bring 4% of it.

The nearest other station, San Luis Obispo Airport, CA, 32 miles west of Santa Margarita and 382 feet lower, has a last frost 4 days earlier (January 31), a first frost 7 days later (December 11), a season 18 days longer.

Measurable snow is rare here: only 0 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Santa Margarita Boost, CA, 31.4 miles away, so there is no typical first-snow date to plan around.

ZIP 93453 is 27 miles from Twitchell Dam, CA, which stands at 582 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. That is farther than 25 miles, so local frost can differ noticeably from these figures. The 2023 USDA Plant Hardiness Zone Map lists ZIP 93453 in zone 8b, the band where the coldest night of the year averaged 15 to 20°F (-9.4 to -6.7°C) over 1991–2020; a zone describes winter lows, not frost dates.