USDA Hardiness Zone 9a
Frost Dates for 95631 — Foresthill, California
NOAA 1991–2020 normals from Georgetown Rs, CA (3,001 ft), 7 miles south.
Updated
In Foresthill, the last spring frost (32°F) is around April 12 in half of years and has passed by May 10 in nine years out of ten. The first fall frost comes around November 21, as early as October 29 one year in ten, leaving a typical freeze-free season of 221 days (NOAA, Georgetown Rs, CA).
- Last spring frost
- April 12
- First fall frost
- November 21
- Growing season
- 221 days
- Hardiness zone
- 9a
50% probability
50% probability
freeze-free, 50%
20 to 25°F (-6.7 to -3.9°C) coldest night
- First snow
- Rare
- Last snow
- Rare
- Winters with snow
- 44%
- Snow per year
- 2.6"
median, 1991–2020
median, 1991–2020
11 of 25 observed
NOAA normal
Frost risk by date in Foresthill
Half of springs at Georgetown Rs, CA see their last 32°F night by April 12; only one in ten is past it by March 13, and one in ten still has one after May 10. Planting tender crops after April 20 leaves a 30% risk of a frost on them, after April 27 20%, and after May 10 10%. The 28 days between the even-odds date and the one-in-ten date is narrower than at 60% 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 21 in half of years, as early as October 29 one year in ten, and holds off past December 9 one year in ten. A hard freeze of 28°F follows 17 days later, around December 8; in spring the one-in-ten date for 28°F is April 14, 26 days before the 32°F one. The freeze-free season lasts 221 days in a typical year, shorter than at 75% of the 219 California stations; it reaches 255 days one year in ten and falls short of 182 one year in ten. On average 49 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 19 days longer, to about May 1, and return around November 3. Nights of 24°F, cold enough to damage hardier plants, come in 80% of winters and 16°F in 7%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 11 | Apr 18 | Apr 22 | Apr 26 | May 1 | May 5 | May 11 | May 18 | May 27 |
| 32°F | Mar 13 | Mar 28 | Apr 3 | Apr 8 | Apr 12 | Apr 16 | Apr 20 | Apr 27 | May 10 |
| 28°F99% of yrs | Jan 31 | Feb 18 | Feb 28 | Mar 6 | Mar 13 | Mar 21 | Mar 30 | Apr 5 | Apr 14 |
| 24°F80% of yrs | Dec 22 | Jan 6 | Jan 17 | Jan 29 | Feb 8 | Feb 18 | Feb 27 | Mar 5 | Mar 19 |
| 20°F31% of yrs | too rare for a date | ||||||||
| 16°F7% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 9 | Oct 18 | Oct 24 | Oct 30 | Nov 3 | Nov 9 | Nov 13 | Nov 17 | Nov 22 |
| 32°F | Oct 29 | Nov 5 | Nov 12 | Nov 16 | Nov 21 | Nov 24 | Nov 28 | Dec 3 | Dec 9 |
| 28°F99% of yrs | Nov 18 | Nov 24 | Nov 30 | Dec 4 | Dec 8 | Dec 12 | Dec 17 | Dec 26 | Jan 6 |
| 24°F80% of yrs | Dec 1 | Dec 10 | Dec 20 | Dec 28 | Jan 1 | Jan 9 | Jan 20 | Feb 1 | Feb 18 |
| 20°F31% of yrs | too rare for a date | ||||||||
| 16°F7% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Georgetown Rs, 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 95631 →Compare Foresthill with another place →
Weather by month in Foresthill
July is the warmest month at Georgetown Rs, CA, averaging 91°F by day and 63°F at night; December is the coldest at 50°F and 36°F. A freezing night is all but certain in every month from December to February (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, March still brings one in 88% of years and April still brings one in 70% of years and May still brings one in 18% of years.
Warmth for growing adds up to 3,939 growing degree days a year (base 50°F), fewer than at 62% of the 283 California stations. 29% of them (1,157) have built up by the end of June, and July adds the most, 831.
| Month | High °F | Low °F | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|
| Jan | 52 | 36 | 94% | 11 | 27 |
| Feb | 55 | 36 | 94% | 9 | 35 |
| Mar | 59 | 38 | 88% | 8 | 72 |
| Apr | 64 | 41 | 70% | 4 | 140 |
| May | 72 | 48 | 18% | <1 | 316 |
| Jun | 82 | 56 | 0% | 0 | 567 |
| Jul | 91 | 63 | 0% | 0 | 831 |
| Aug | 91 | 63 | 0% | 0 | 823 |
| Sep | 86 | 57 | 1% | <1 | 645 |
| Oct | 74 | 49 | 12% | <1 | 375 |
| Nov | 59 | 41 | 70% | 5 | 95 |
| Dec | 50 | 36 | 99% | 11 | 13 |
Monthly normals 1991–2020 at Georgetown Rs, CA (3,001 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, Colfax, CA, 8 miles northwest of Foresthill and 621 feet lower, has a last frost 9 days earlier (April 3), a first frost 3 days later (November 24), a season 12 days longer.
When it snows in Foresthill, California
Measurable snow is rare here: only 11 of 25 winters from 1991 to 2020 recorded 0.1 inch or more at Foresthill Rs, CA, 2.1 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 95631
| When | What to do |
|---|---|
| February 1 – February 15 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 15 – March 1 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 15 – March 29 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 12 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 29 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by November 7 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 21 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 95631 is 7 miles from Georgetown Rs, CA, which stands at 3,001 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 95631 in zone 9a, the band where the coldest night of the year averaged 20 to 25°F (-6.7 to -3.9°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.