USDA Hardiness Zone 9b
Frost Dates for 95669 — Plymouth, California
NOAA 1991–2020 normals from Sutter Hill Cdf, CA (1,586 ft), 8 miles southeast.
Updated
In Plymouth, the last spring frost (32°F) is around March 4 in half of years and has passed by April 8 in nine years out of ten. The first fall frost comes around December 11, as early as November 19 one year in ten, leaving a typical freeze-free season of 285 days (NOAA, Sutter Hill Cdf, CA).
- Last spring frost
- March 4
- First fall frost
- December 11
- Growing season
- 285 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
- 13%
- Snow per year
- —
median, 1991–2020
median, 1991–2020
2 of 16 observed
NOAA normal
Frost risk by date in Plymouth
Half of springs at Sutter Hill Cdf, CA see their last 32°F night by March 4; only one in ten is past it by January 6, and one in ten still has one after April 8. Planting tender crops after March 21 leaves a 30% risk of a frost on them, after March 31 20%, and after April 8 10%. The 35 days between the even-odds date and the one-in-ten date is wider than at 71% 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 11 in half of years, as early as November 19 one year in ten, and holds off past January 4 one year in ten. A hard freeze of 28°F follows 16 days later, around December 27; in spring the one-in-ten date for 28°F is March 2, 37 days before the 32°F one. The freeze-free season lasts 285 days in a typical year, longer than at 56% of the 219 California stations; it reaches 343 days one year in ten and falls short of 234 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 37 days longer, to about April 10, and return around November 25. A 24°F night is unusual: 17% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 9 | Mar 23 | Mar 31 | Apr 5 | Apr 10 | Apr 15 | Apr 20 | Apr 26 | May 4 |
| 32°F99% of yrs | Jan 6 | Jan 21 | Feb 4 | Feb 20 | Mar 4 | Mar 13 | Mar 21 | Mar 31 | Apr 8 |
| 28°F62% of yrs | Dec 14 | Dec 26 | Dec 31 | Jan 5 | Jan 10 | Jan 14 | Jan 24 | Feb 2 | Mar 2 |
| 24°F17% of yrs | too rare for a date | ||||||||
| 20°F1% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 1 | Nov 11 | Nov 17 | Nov 21 | Nov 25 | Nov 30 | Dec 3 | Dec 7 | Dec 12 |
| 32°F99% of yrs | Nov 19 | Nov 27 | Dec 2 | Dec 7 | Dec 11 | Dec 15 | Dec 20 | Dec 26 | Jan 4 |
| 28°F62% of yrs | Dec 2 | Dec 9 | Dec 14 | Dec 20 | Dec 27 | Jan 1 | Jan 6 | Jan 12 | Jan 26 |
| 24°F17% of yrs | too rare for a date | ||||||||
| 20°F1% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Sutter Hill Cdf, 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 95669 →Compare Plymouth with another place →
Weather by month in Plymouth
July is the warmest month at Sutter Hill Cdf, CA, averaging 93°F by day and 63°F at night; December is the coldest at 55°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 41% of years and March still brings one in 42% of years and April still brings one in 17% of years.
Warmth for growing adds up to 4,486 growing degree days a year (base 50°F), fewer than at 53% of the 283 California stations. 32% of them (1,456) have built up by the end of June, and July adds the most, 868.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 55 | 39 | 74% | 5 | 34 |
| Feb | 58 | 42 | 41% | 3 | 62 |
| Mar | 62 | 42 | 42% | 1 | 115 |
| Apr | 67 | 45 | 17% | 1 | 198 |
| May | 75 | 51 | 2% | 0 | 404 |
| Jun | 86 | 57 | 0% | 0 | 644 |
| Jul | 93 | 63 | 0% | 0 | 868 |
| Aug | 92 | 62 | 0% | 0 | 834 |
| Sep | 87 | 60 | 0% | 0 | 693 |
| Oct | 77 | 53 | 3% | <1 | 457 |
| Nov | 63 | 44 | 23% | 1 | 149 |
| Dec | 55 | 39 | 78% | 5 | 30 |
Monthly normals 1991–2020 at Sutter Hill Cdf, CA (1,586 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, Placerville, CA, 15 miles north of Plymouth and 264 feet higher, has a last frost 27 days later (March 31), a first frost 20 days earlier (November 21), a season 48 days shorter.
When it snows in Plymouth, California
Measurable snow is rare here: only 2 of 16 winters from 1991 to 2020 recorded 0.1 inch or more at Sutter Hill Cdf, CA, 8 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 95669
| When | What to do |
|---|---|
| December 24 – January 7 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| January 7 – January 21 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| February 4 – February 18 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| March 4 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 18 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 27 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 11 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 95669 is 8 miles from Sutter Hill Cdf, CA, which stands at 1,586 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 95640 (Ione). The 2023 USDA Plant Hardiness Zone Map lists ZIP 95669 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.