USDA Hardiness Zone 10a
Frost Dates for 92251 — Imperial, California
NOAA 1991–2020 normals from Imperial, CA, 1 miles east.
Updated
A freeze (32°F) reaches Imperial in 61% of winters. When it does, the first fall frost comes around December 26 and the last spring frost around January 4; after February 7 the chance of another is under 6%.
- Last spring frost
- January 4
- First fall frost
- December 26
- Winters with a freeze
- 61%
- 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 24 observed
NOAA normal
Frost risk by date in Imperial
In the 61% of winters that bring a 32°F night, half of springs at Imperial, CA see their last 32°F night by January 4; 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 6% and after January 4 30%. The 34 days between the even-odds date and the one-in-ten date is wider than at 65% 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 26 in half of years, as early as December 6 one year in ten, and holds off past January 25 one year in ten. A hard freeze of 28°F is less common: it came in 12% of winters. The freeze-free season lasts 360 days in a typical year, longer than at 98% of the 219 California stations; it reaches 365 days one year in ten and falls short of 330 one year in ten. On average 4 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 20 days longer, to about January 24, and return around December 14. A 24°F night is unusual: 0% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F96% of yrs | Dec 28 | Jan 4 | Jan 10 | Jan 16 | Jan 24 | Jan 31 | Feb 4 | Feb 11 | Feb 21 |
| 32°F61% of yrs | Dec 13 | Dec 22 | Dec 28 | Dec 31 | Jan 4 | Jan 8 | Jan 16 | Jan 26 | Feb 7 |
| 28°F12% of yrs | too rare for a date | ||||||||
| 24°F0% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F96% of yrs | Nov 27 | Dec 1 | Dec 6 | Dec 10 | Dec 14 | Dec 18 | Dec 21 | Dec 25 | Jan 1 |
| 32°F61% of yrs | Dec 6 | Dec 12 | Dec 18 | Dec 22 | Dec 26 | Dec 30 | Jan 2 | Jan 9 | Jan 25 |
| 28°F12% of yrs | too rare for a date | ||||||||
| 24°F0% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Imperial, 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 92251 →Compare Imperial with another place →
Weather by month in Imperial
August is the warmest month at Imperial, CA, averaging 105°F by day and 78°F at night; December is the coldest at 68°F and 42°F. From February to November the chance of a 32°F night stays under 10% each month.
Warmth for growing adds up to 8,448 growing degree days a year (base 50°F), more than at 97% of the 283 California stations. 41% of them (3,457) have built up by the end of June, and August adds the most, 1,285. Precipitation totals 2.8 inches a year, most in January (0.5") and least in June (0.0"); May to September bring 25% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 69 | 43 | 0.5 | 29% | 1 | 196 |
| Feb | 72 | 47 | 0.4 | 10% | <1 | 265 |
| Mar | 78 | 52 | 0.3 | 0% | 0 | 463 |
| Apr | 84 | 56 | 0.1 | 0% | 0 | 611 |
| May | 93 | 63 | 0.1 | 0% | 0 | 860 |
| Jun | 101 | 70 | 0.0 | 0% | 0 | 1062 |
| Jul | 104 | 77 | 0.1 | 0% | 0 | 1266 |
| Aug | 105 | 78 | 0.2 | 0% | 0 | 1285 |
| Sep | 100 | 73 | 0.3 | 0% | 0 | 1096 |
| Oct | 89 | 61 | 0.2 | 0% | 0 | 780 |
| Nov | 77 | 50 | 0.2 | 2% | <1 | 399 |
| Dec | 68 | 42 | 0.4 | 39% | 2 | 165 |
Monthly normals 1991–2020 at Imperial, CA, 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, El Centro 2 SSW, CA, 6 miles south of Imperial, has a last frost 1 day earlier (January 3), a first frost 1 day later (December 27), a season 3 days longer.
When it snows in Imperial, California
Measurable snow is rare here: only 0 of 24 winters from 1991 to 2020 recorded 0.1 inch or more at Imperial, CA, 1.4 miles away, so there is no typical first-snow date to plan around.
Where these figures come from
ZIP 92251 is 1 mile from Imperial, CA, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 92251 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.