USDA Hardiness Zone 9b
Frost Dates for 95442 — Glen Ellen, California
NOAA 1991–2020 normals from Sonoma, CA (97 ft), 6 miles southeast.
Updated
In Glen Ellen, the last spring frost (32°F) is around March 2 in half of years and has passed by April 5 in nine years out of ten. The first fall frost comes around November 27, as early as November 6 one year in ten, leaving a typical freeze-free season of 270 days (NOAA, Sonoma, CA).
- Last spring frost
- March 2
- First fall frost
- November 27
- Growing season
- 270 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
- 0%
- Snow per year
- 0"
median, 1991–2020
median, 1991–2020
0 of 20 observed
NOAA normal
Frost risk by date in Glen Ellen
Half of springs at Sonoma, CA see their last 32°F night by March 2; only one in ten is past it by January 27, and one in ten still has one after April 5. Planting tender crops after March 13 leaves a 30% risk of a frost on them, after March 23 20%, and after April 5 10%. 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 November 27 in half of years, as early as November 6 one year in ten, and holds off past December 21 one year in ten. A hard freeze of 28°F follows 17 days later, around December 14; in spring the one-in-ten date for 28°F is February 22, 42 days before the 32°F one. The freeze-free season lasts 270 days in a typical year, shorter than at 58% of the 219 California stations; it reaches 310 days one year in ten and falls short of 230 one year in ten. On average 21 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 8, and return around November 8. A 24°F night is unusual: 36% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Mar 14 | Mar 24 | Mar 30 | Apr 3 | Apr 8 | Apr 14 | Apr 18 | Apr 24 | Apr 29 |
| 32°F | Jan 27 | Feb 7 | Feb 17 | Feb 25 | Mar 2 | Mar 6 | Mar 13 | Mar 23 | Apr 5 |
| 28°F87% of yrs | Dec 20 | Dec 29 | Jan 4 | Jan 12 | Jan 20 | Jan 27 | Feb 1 | Feb 11 | Feb 22 |
| 24°F36% of yrs | too rare for a date | ||||||||
| 20°F2% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 25 | Oct 30 | Nov 1 | Nov 4 | Nov 8 | Nov 10 | Nov 14 | Nov 19 | Nov 26 |
| 32°F | Nov 6 | Nov 12 | Nov 18 | Nov 23 | Nov 27 | Dec 1 | Dec 4 | Dec 10 | Dec 21 |
| 28°F87% of yrs | Nov 24 | Dec 1 | Dec 5 | Dec 9 | Dec 14 | Dec 19 | Dec 27 | Jan 4 | Jan 17 |
| 24°F36% of yrs | too rare for a date | ||||||||
| 20°F2% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Sonoma, 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 95442 →Compare Glen Ellen with another place →
Weather by month in Glen Ellen
July is the warmest month at Sonoma, CA, averaging 86°F by day and 54°F at night; December is the coldest at 57°F and 38°F. From May to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 73% of years and March still brings one in 43% of years and April still brings one in 13% of years.
Warmth for growing adds up to 3,608 growing degree days a year (base 50°F), fewer than at 70% of the 283 California stations. 36% of them (1,303) have built up by the end of June, and July adds the most, 612. Precipitation totals 28.3 inches a year, most in December (5.8") and least in July (0.0"); May to September bring 5% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 57 | 38 | 5.5 | 83% | 7 | 26 |
| Feb | 62 | 40 | 5.4 | 73% | 4 | 67 |
| Mar | 65 | 42 | 3.8 | 43% | 1 | 135 |
| Apr | 69 | 44 | 1.8 | 13% | <1 | 205 |
| May | 75 | 48 | 1.0 | 0% | 0 | 359 |
| Jun | 83 | 51 | 0.3 | 0% | 0 | 512 |
| Jul | 86 | 54 | 0.0 | 0% | 0 | 612 |
| Aug | 86 | 53 | 0.1 | 0% | 0 | 609 |
| Sep | 85 | 51 | 0.1 | 0% | 0 | 540 |
| Oct | 78 | 47 | 1.5 | 3% | 0 | 386 |
| Nov | 65 | 42 | 3.0 | 55% | 2 | 131 |
| Dec | 57 | 38 | 5.8 | 84% | 8 | 27 |
Monthly normals 1991–2020 at Sonoma, CA (97 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, Petaluma Airport, CA, 9 miles southwest of Glen Ellen, has a last frost 2 days earlier (February 28), a first frost 2 days earlier (November 25), a season 1 day longer.
When it snows in Glen Ellen, California
Measurable snow is rare here: only 0 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Sonoma, CA, 5.8 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 95442
| When | What to do |
|---|---|
| December 22 – January 5 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| January 5 – January 19 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| February 2 – February 16 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| March 2 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 4 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 13 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 27 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 95442 is 6 miles from Sonoma, CA, which stands at 97 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 95476 (Sonoma). The 2023 USDA Plant Hardiness Zone Map lists ZIP 95442 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.