Frost Dates for 92040 — Lakeside, California

In the 73% of winters that bring a 32°F night, half of springs at El Cajon, CA see their last 32°F night by January 6; only one in ten is past it by December 13, and one in ten still has one after February 7. Counting the winters with no freeze at all, the risk of a 32°F night after February 7 is under 7% and after January 6 36%. The 32 days between the even-odds date and the one-in-ten date is wider than at 55% 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 21 in half of years, as early as December 1 one year in ten, and holds off past January 15 one year in ten. A hard freeze of 28°F is less common: it came in 16% of winters. The freeze-free season lasts 350 days in a typical year, longer than at 94% of the 219 California stations; it reaches 365 days one year in ten and falls short of 317 one year in ten. On average 3 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 31 days longer, to about February 6, and return around December 6. No night reached 24°F in 1991–2020.

August is the warmest month at El Cajon, CA, averaging 89°F by day and 65°F at night; December is the coldest at 69°F and 42°F. From March to November the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 12% of years.

Warmth for growing adds up to 5,564 growing degree days a year (base 50°F), more than at 81% of the 283 California stations. 39% of them (2,162) have built up by the end of June, and August adds the most, 826. Precipitation totals 11.6 inches a year, most in February (2.6") and least in August (0.0"); May to September bring 6% of it.

The nearest other station, Alpine, CA, 8 miles east of Lakeside and 1,200 feet higher, has a last frost 37 days later (February 12), a first frost 3 days later (December 24), a season 33 days shorter.

Measurable snow is rare here: only 0 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Lakeside 2 E, CA, 1.5 miles away, so there is no typical first-snow date to plan around.

ZIP 92040 is 5 miles from El Cajon, CA, which stands at 495 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 10 other ZIP codes share the station; its figures are presented in full for 92021 (El Cajon). The 2023 USDA Plant Hardiness Zone Map lists ZIP 92040 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.