USDA Hardiness Zone 10a
Frost Dates for 92020 — El Cajon, California
NOAA 1991–2020 normals from El Cajon, CA (495 ft), 3 miles east.
Updated
A freeze (32°F) reaches El Cajon in 73% of winters. When it does, the first fall frost comes around December 21 and the last spring frost around January 6; after February 7 the chance of another is under 7%.
- Last spring frost
- January 6
- First fall frost
- December 21
- Winters with a freeze
- 73%
- Hardiness zone
- 10a
50%, in freezing years
50%, in freezing years
32°F or below, 1991–2020
30 to 35°F (-1.1 to 1.7°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 0%
- Snow per year
- 0"
median, 1991–2020
median, 1991–2020
0 of 18 observed
NOAA normal
Frost risk by date in El Cajon
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.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F99% of yrs | Jan 6 | Jan 16 | Jan 25 | Jan 31 | Feb 6 | Feb 12 | Feb 18 | Feb 25 | Mar 3 |
| 32°F73% of yrs | Dec 13 | Dec 22 | Dec 28 | Dec 31 | Jan 6 | Jan 12 | Jan 21 | Jan 30 | Feb 7 |
| 28°F16% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F99% of yrs | Nov 18 | Nov 25 | Nov 29 | Dec 2 | Dec 6 | Dec 10 | Dec 15 | Dec 20 | Dec 29 |
| 32°F73% of yrs | Dec 1 | Dec 7 | Dec 12 | Dec 17 | Dec 21 | Dec 25 | Dec 30 | Jan 4 | Jan 15 |
| 28°F16% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at El Cajon, CA, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 92020 →Compare El Cajon with another place →
Weather by month in El Cajon
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.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 69 | 43 | 2.3 | 36% | 1 | 189 |
| Feb | 69 | 44 | 2.6 | 12% | <1 | 194 |
| Mar | 71 | 48 | 1.9 | 0% | 0 | 300 |
| Apr | 75 | 51 | 0.8 | 0% | 0 | 378 |
| May | 76 | 56 | 0.3 | 0% | 0 | 498 |
| Jun | 81 | 59 | 0.1 | 0% | 0 | 603 |
| Jul | 86 | 63 | 0.2 | 0% | 0 | 766 |
| Aug | 89 | 65 | 0.0 | 0% | 0 | 826 |
| Sep | 87 | 62 | 0.1 | 0% | 0 | 741 |
| Oct | 81 | 56 | 0.5 | 0% | 0 | 567 |
| Nov | 75 | 47 | 1.0 | 5% | <1 | 336 |
| Dec | 69 | 42 | 1.8 | 50% | 1 | 166 |
Monthly normals 1991–2020 at El Cajon, CA (495 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, San Diego Montgomery Field, CA, 10 miles west of El Cajon, has a 32°F night in 6% of winters against 73% here, and a coolest-month low 3°F warmer (45°F).
When it snows in El Cajon, California
Measurable snow is rare here: only 0 of 18 winters from 1991 to 2020 recorded 0.1 inch or more at El Cajon, CA, 2.6 miles away, so there is no typical first-snow date to plan around.
Where these figures come from
ZIP 92020 is 3 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 92020 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.
Frost dates across California →
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.