USDA Hardiness Zone 10a
Frost Dates for 92078 — San Marcos, California
NOAA 1991–2020 normals from Escondido #2, CA (600 ft), 4 miles east.
Updated
Frost is not a yearly event in San Marcos: a night at or below 32°F came in 39% of the winters of 1991–2020 at Escondido #2, CA, and a 36°F night, cold enough for frost on exposed leaves, in 94%. There is no reliable "last frost date" here; most years have none.
- Winters with a freeze
- 39%
- Winters with 36°F
- 94%
- Coldest month low
- 44°F
- Hardiness zone
- 10a
32°F or below, 1991–2020
frost possible on leaves
average, December
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 17 observed
NOAA normal
Frost risk by date in San Marcos
At Escondido #2, CA, 4 miles east of San Marcos, 39% of the winters of 1991–2020 had at least one night at or below 32°F, 3% reached 28°F. Nights of 36°F, enough for frost on exposed leaves, are more common (94% of winters) and, when they come, fall between about December 18 and January 31. December is the month most likely to bring one: a 21% chance in a given year. 62 of the 283 other California stations behind this site's ZIP pages freeze in fewer than half of winters too.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F94% of yrs | Dec 29 | Jan 5 | Jan 13 | Jan 21 | Jan 31 | Feb 5 | Feb 13 | Feb 21 | Mar 1 |
| 32°F39% of yrs | too rare for a date | ||||||||
| 28°F3% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F94% of yrs | Nov 27 | Dec 4 | Dec 10 | Dec 14 | Dec 18 | Dec 22 | Dec 26 | Jan 1 | Jan 19 |
| 32°F39% of yrs | too rare for a date | ||||||||
| 28°F3% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Escondido #2, 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 92078 →Compare San Marcos with another place →
Weather by month in San Marcos
August is the warmest month at Escondido #2, CA, averaging 89°F by day and 65°F at night; December is the coldest at 68°F and 44°F. From February to November the chance of a 32°F night stays under 10% each month.
Warmth for growing adds up to 5,796 growing degree days a year (base 50°F), more than at 86% of the 283 California stations. 39% of them (2,268) have built up by the end of June, and August adds the most, 842. Precipitation totals 14.7 inches a year, most in February (3.6") and least in June (0.1"); 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 | 45 | 3.2 | 16% | 1 | 216 |
| Feb | 69 | 46 | 3.6 | 5% | <1 | 208 |
| Mar | 71 | 49 | 2.2 | 0% | 0 | 309 |
| Apr | 74 | 52 | 1.0 | 0% | 0 | 390 |
| May | 77 | 56 | 0.4 | 0% | 0 | 513 |
| Jun | 82 | 60 | 0.1 | 0% | 0 | 632 |
| Jul | 87 | 64 | 0.1 | 0% | 0 | 800 |
| Aug | 89 | 65 | 0.1 | 0% | 0 | 842 |
| Sep | 87 | 63 | 0.2 | 0% | 0 | 750 |
| Oct | 81 | 57 | 0.6 | 0% | 0 | 591 |
| Nov | 75 | 49 | 1.1 | 1% | <1 | 356 |
| Dec | 68 | 44 | 2.1 | 21% | 1 | 189 |
Monthly normals 1991–2020 at Escondido #2, CA (600 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, Carlsbad Palomar Airport, CA, 7 miles west of San Marcos and 272 feet lower, has a 32°F night in 1% of winters against 39% here, and a coolest-month low 3°F warmer (47°F).
When it snows in San Marcos, California
Measurable snow is rare here: only 0 of 17 winters from 1991 to 2020 recorded 0.1 inch or more at Escondido #2, CA, 3.8 miles away, so there is no typical first-snow date to plan around.
Where these figures come from
ZIP 92078 is 4 miles from Escondido #2, CA, which stands at 600 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 5 other ZIP codes share the station; its figures are presented in full for 92027 (Escondido). The 2023 USDA Plant Hardiness Zone Map lists ZIP 92078 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.