USDA Hardiness Zone 10a
Frost Dates for 92405 — San Bernardino, California
NOAA 1991–2020 normals from Redlands, CA (1,410 ft), 9 miles southeast.
Updated
A freeze (32°F) reaches San Bernardino in 88% of winters. When it does, the first fall frost comes around December 19 and the last spring frost around January 27; after February 28 the chance of another is under 9%.
- Last spring frost
- January 27
- First fall frost
- December 19
- Winters with a freeze
- 88%
- 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 San Bernardino
In the 88% of winters that bring a 32°F night, half of springs at Redlands, CA see their last 32°F night by January 27; only one in ten is past it by December 21, and one in ten still has one after February 28. Counting the winters with no freeze at all, the risk of a 32°F night after February 28 is under 9% and after January 27 44%. 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 19 in half of years, as early as December 1 one year in ten, and holds off past January 26 one year in ten. A hard freeze of 28°F is less common: it came in 26% of winters. The freeze-free season lasts 329 days in a typical year, longer than at 81% of the 219 California stations; it reaches 365 days one year in ten and falls short of 292 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 34 days longer, to about March 2, and return around December 2. A 24°F night is unusual: 0% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jan 31 | Feb 10 | Feb 19 | Feb 26 | Mar 2 | Mar 7 | Mar 13 | Mar 22 | Apr 5 |
| 32°F88% of yrs | Dec 21 | Jan 1 | Jan 7 | Jan 16 | Jan 27 | Feb 3 | Feb 10 | Feb 19 | Feb 28 |
| 28°F26% 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°F | Nov 17 | Nov 22 | Nov 26 | Nov 30 | Dec 2 | Dec 5 | Dec 9 | Dec 14 | Dec 19 |
| 32°F88% of yrs | Dec 1 | Dec 6 | Dec 11 | Dec 15 | Dec 19 | Dec 25 | Jan 1 | Jan 9 | Jan 26 |
| 28°F26% of yrs | too rare for a date | ||||||||
| 24°F0% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Redlands, 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 92405 →Compare San Bernardino with another place →
Weather by month in San Bernardino
August is the warmest month at Redlands, CA, averaging 96°F by day and 63°F at night; December is the coldest at 67°F and 40°F. From March to November the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 34% of years.
Warmth for growing adds up to 5,663 growing degree days a year (base 50°F), more than at 83% of the 283 California stations. 37% of them (2,079) have built up by the end of June, and August adds the most, 916. Precipitation totals 12.9 inches a year, most in February (3.0") 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 | 67 | 41 | 2.8 | 51% | 1 | 146 |
| Feb | 67 | 42 | 3.0 | 34% | <1 | 151 |
| Mar | 71 | 45 | 2.0 | 7% | 0 | 249 |
| Apr | 76 | 48 | 0.9 | 1% | 0 | 352 |
| May | 80 | 52 | 0.4 | 0% | 0 | 507 |
| Jun | 89 | 56 | 0.1 | 0% | 0 | 674 |
| Jul | 95 | 63 | 0.1 | 0% | 0 | 897 |
| Aug | 96 | 63 | 0.1 | 0% | 0 | 916 |
| Sep | 92 | 60 | 0.1 | 0% | 0 | 778 |
| Oct | 83 | 53 | 0.5 | 0% | 0 | 555 |
| Nov | 75 | 45 | 0.9 | 8% | <1 | 309 |
| Dec | 67 | 40 | 2.0 | 57% | 1 | 129 |
Monthly normals 1991–2020 at Redlands, CA (1,410 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, Lake Arrowhead, CA, 10 miles northeast of San Bernardino and 3,795 feet higher, has a last frost 98 days later (May 5), a first frost 47 days earlier (November 2), a season 153 days shorter.
When it snows in San Bernardino, California
Measurable snow is rare here: only 0 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Redlands, CA, 9.3 miles away, so there is no typical first-snow date to plan around.
Where these figures come from
ZIP 92405 is 9 miles from Redlands, CA, which stands at 1,410 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 13 other ZIP codes share the station; its figures are presented in full for 92346 (Highland). The 2023 USDA Plant Hardiness Zone Map lists ZIP 92405 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.