USDA Hardiness Zone 10a
Frost Dates for 92620 — Irvine, California
NOAA 1991–2020 normals from Tustin Irvine Rch, CA (235 ft), 1 miles southeast.
Updated
A freeze (32°F) reaches Irvine in 50% of winters. When it does, the first fall frost comes around December 25 and the last spring frost around January 5; after February 2 the chance of another is under 5%.
- Last spring frost
- January 5
- First fall frost
- December 25
- Winters with a freeze
- 50%
- 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 20 observed
NOAA normal
Frost risk by date in Irvine
In the 50% of winters that bring a 32°F night, half of springs at Tustin Irvine Rch, CA see their last 32°F night by January 5; only one in ten is past it by December 14, and one in ten still has one after February 2. Counting the winters with no freeze at all, the risk of a 32°F night after February 2 is under 5% and after January 5 25%. The 28 days between the even-odds date and the one-in-ten date is narrower than at 60% 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 25 in half of years, as early as December 3 one year in ten, and holds off past January 20 one year in ten. A hard freeze of 28°F is less common: it came in 7% of winters. The freeze-free season lasts 365 days in a typical year, the longest of the 220 California stations; it reaches 365 days one year in ten and falls short of 331 one year in ten. On average 2 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 27 days longer, to about February 1, and return around December 13. A 24°F night is unusual: 1% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F98% of yrs | Jan 3 | Jan 10 | Jan 17 | Jan 25 | Feb 1 | Feb 6 | Feb 13 | Feb 24 | Mar 5 |
| 32°F50% of yrs | Dec 14 | Dec 22 | Dec 28 | Dec 31 | Jan 5 | Jan 9 | Jan 14 | Jan 23 | Feb 2 |
| 28°F7% of yrs | too rare for a date | ||||||||
| 24°F1% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F98% of yrs | Nov 24 | Dec 1 | Dec 5 | Dec 9 | Dec 13 | Dec 17 | Dec 22 | Dec 31 | Jan 8 |
| 32°F50% of yrs | Dec 3 | Dec 9 | Dec 13 | Dec 19 | Dec 25 | Dec 30 | Jan 3 | Jan 9 | Jan 20 |
| 28°F7% of yrs | too rare for a date | ||||||||
| 24°F1% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Tustin Irvine Rch, 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 92620 →Compare Irvine with another place →
Weather by month in Irvine
August is the warmest month at Tustin Irvine Rch, CA, averaging 87°F by day and 63°F at night; January is the coldest at 68°F and 43°F. From February to November the chance of a 32°F night stays under 10% each month.
Warmth for growing adds up to 5,449 growing degree days a year (base 50°F), more than at 78% of the 283 California stations. 38% of them (2,084) have built up by the end of June, and August adds the most, 781. Precipitation totals 14.2 inches a year, most in February (3.4") and least in July (0.0"); May to September bring 4% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 68 | 43 | 3.1 | 26% | 1 | 179 |
| Feb | 69 | 45 | 3.4 | 5% | 0 | 195 |
| Mar | 72 | 48 | 2.1 | 1% | 0 | 303 |
| Apr | 74 | 50 | 0.8 | 0% | 0 | 357 |
| May | 77 | 55 | 0.3 | 0% | 0 | 484 |
| Jun | 80 | 58 | 0.1 | 0% | 0 | 567 |
| Jul | 85 | 61 | 0.0 | 0% | 0 | 721 |
| Aug | 87 | 63 | 0.0 | 0% | 0 | 781 |
| Sep | 87 | 61 | 0.2 | 0% | 0 | 718 |
| Oct | 84 | 55 | 0.7 | 0% | 0 | 595 |
| Nov | 76 | 47 | 1.2 | 3% | 1 | 349 |
| Dec | 70 | 43 | 2.3 | 30% | 1 | 201 |
Monthly normals 1991–2020 at Tustin Irvine Rch, CA (235 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, Irvine Rch, CA, 2 miles east of Irvine and 305 feet higher, has a 32°F night in 4% of winters against 50% here, and a coolest-month low 5°F warmer (48°F).
When it snows in Irvine, California
Measurable snow is rare here: only 0 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Santa Ana Fire Stn, CA, 6.3 miles away, so there is no typical first-snow date to plan around.
Where these figures come from
ZIP 92620 is 1 mile from Tustin Irvine Rch, CA, which stands at 235 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 7 other ZIP codes share the station; its figures are presented in full for 92630 (Lake Forest). The 2023 USDA Plant Hardiness Zone Map lists ZIP 92620 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.