USDA Hardiness Zone 9b
Frost Dates for 94508 — Angwin, California
NOAA 1991–2020 normals from Angwin Pacific Union College, CA (1,715 ft), under a mile northeast.
Updated
In Angwin, the last spring frost (32°F) is around April 7 in half of years and has passed by April 30 in nine years out of ten. The first fall frost comes around December 5, as early as November 14 one year in ten, leaving a typical freeze-free season of 245 days (NOAA, Angwin Pacific Union College, CA).
- Last spring frost
- April 7
- First fall frost
- December 5
- Growing season
- 245 days
- Hardiness zone
- 9b
50% probability
50% probability
freeze-free, 50%
25 to 30°F (-3.9 to -1.1°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 5%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
1 of 20 observed
NOAA normal
Frost risk by date in Angwin
Half of springs at Angwin Pacific Union College, CA see their last 32°F night by April 7; only one in ten is past it by February 23, and one in ten still has one after April 30. Planting tender crops after April 18 leaves a 30% risk of a frost on them, after April 23 20%, and after April 30 10%. The 23 days between the even-odds date and the one-in-ten date is narrower than at 78% 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 5 in half of years, as early as November 14 one year in ten, and holds off past January 1 one year in ten. A hard freeze of 28°F follows 25 days later, around December 30; in spring the one-in-ten date for 28°F is April 9, 21 days before the 32°F one. The freeze-free season lasts 245 days in a typical year, shorter than at 68% of the 219 California stations; it reaches 293 days one year in ten and falls short of 209 one year in ten. On average 15 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 23 days longer, to about April 30, and return around November 15. A 24°F night is unusual: 20% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 6 | Apr 16 | Apr 21 | Apr 26 | Apr 30 | May 4 | May 9 | May 15 | May 25 |
| 32°F | Feb 23 | Mar 9 | Mar 21 | Mar 31 | Apr 7 | Apr 13 | Apr 18 | Apr 23 | Apr 30 |
| 28°F83% of yrs | Dec 23 | Jan 4 | Jan 19 | Feb 3 | Feb 18 | Mar 2 | Mar 15 | Mar 30 | Apr 9 |
| 24°F20% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 22 | Nov 1 | Nov 5 | Nov 10 | Nov 15 | Nov 18 | Nov 23 | Nov 30 | Dec 5 |
| 32°F | Nov 14 | Nov 21 | Nov 27 | Dec 1 | Dec 5 | Dec 9 | Dec 14 | Dec 21 | Jan 1 |
| 28°F83% of yrs | Nov 29 | Dec 6 | Dec 13 | Dec 20 | Dec 30 | Jan 4 | Jan 21 | Feb 4 | Mar 4 |
| 24°F20% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Angwin Pacific Union College, 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 94508 →Compare Angwin with another place →
Weather by month in Angwin
July is the warmest month at Angwin Pacific Union College, CA, averaging 85°F by day and 54°F at night; December is the coldest at 53°F and 39°F. From May to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 68% of years and March still brings one in 67% of years and April still brings one in 55% of years.
Warmth for growing adds up to 3,278 growing degree days a year (base 50°F), fewer than at 77% of the 283 California stations. 34% of them (1,100) have built up by the end of June, and July adds the most, 600. Precipitation totals 39.8 inches a year, most in December (8.3") and least in July (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 | 54 | 39 | 7.8 | 78% | 4 | 33 |
| Feb | 56 | 40 | 7.6 | 68% | 3 | 45 |
| Mar | 60 | 41 | 5.5 | 67% | 2 | 93 |
| Apr | 66 | 42 | 2.4 | 55% | 1 | 154 |
| May | 73 | 47 | 1.6 | 9% | <1 | 306 |
| Jun | 80 | 51 | 0.4 | 0% | 0 | 470 |
| Jul | 85 | 54 | 0.0 | 0% | 0 | 600 |
| Aug | 84 | 54 | 0.0 | 0% | 0 | 592 |
| Sep | 81 | 53 | 0.2 | 0% | 0 | 521 |
| Oct | 72 | 50 | 1.9 | 0% | 0 | 347 |
| Nov | 60 | 43 | 4.1 | 36% | 1 | 98 |
| Dec | 53 | 39 | 8.3 | 83% | 4 | 20 |
Monthly normals 1991–2020 at Angwin Pacific Union College, CA (1,715 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, Saint Helena, CA, 4 miles south of Angwin and 1,490 feet lower, has a last frost 63 days earlier (February 3), a first frost 1 day earlier (December 4), a season 61 days longer.
When it snows in Angwin, California
Measurable snow is rare here: only 1 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Angwin Pacific Union College, CA, 0.6 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 94508
| When | What to do |
|---|---|
| January 27 – February 10 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 10 – February 24 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 10 – March 24 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 7 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 12 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 21 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 5 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 94508 is under a mile from Angwin Pacific Union College, CA, which stands at 1,715 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 94508 in zone 9b, the band where the coldest night of the year averaged 25 to 30°F (-3.9 to -1.1°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.