USDA Hardiness Zone 9b
Frost Dates for 95949 — Grass Valley, California
NOAA 1991–2020 normals from Grass Valley #2, CA (2,400 ft), 5 miles north.
Updated
In Grass Valley, the last spring frost (32°F) is around April 10 in half of years and has passed by April 30 in nine years out of ten. The first fall frost comes around November 13, as early as October 26 one year in ten, leaving a typical freeze-free season of 215 days (NOAA, Grass Valley #2, CA).
- Last spring frost
- April 10
- First fall frost
- November 13
- Growing season
- 215 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
- January 8
- Last snow
- March 5
- Winters with snow
- 81%
- Snow per year
- 8.6"
median, 1991–2020
median, 1991–2020
22 of 27 observed
NOAA normal
Frost risk by date in Grass Valley
Half of springs at Grass Valley #2, CA see their last 32°F night by April 10; only one in ten is past it by March 17, 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 20 days between the even-odds date and the one-in-ten date is narrower than at 88% of the 220 California stations behind this site's ZIP pages.
In fall the first 32°F night comes by November 13 in half of years, as early as October 26 one year in ten, and holds off past December 1 one year in ten. A hard freeze of 28°F follows 18 days later, around December 1; in spring the one-in-ten date for 28°F is April 8, 22 days before the 32°F one. The freeze-free season lasts 215 days in a typical year, shorter than at 76% of the 219 California stations; it reaches 244 days one year in ten and falls short of 188 one year in ten. On average 61 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 18 days longer, to about April 28, and return around October 31. Nights of 24°F, cold enough to damage hardier plants, come in 84% of winters and 16°F in 2%.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Apr 13 | Apr 18 | Apr 22 | Apr 25 | Apr 28 | May 1 | May 5 | May 11 | May 20 |
| 32°F | Mar 17 | Mar 29 | Apr 3 | Apr 7 | Apr 10 | Apr 14 | Apr 18 | Apr 23 | Apr 30 |
| 28°F | Jan 31 | Feb 16 | Feb 25 | Mar 1 | Mar 9 | Mar 15 | Mar 25 | Apr 2 | Apr 8 |
| 24°F84% of yrs | Dec 19 | Dec 30 | Jan 5 | Jan 13 | Jan 21 | Jan 30 | Feb 6 | Feb 16 | Feb 27 |
| 20°F25% of yrs | too rare for a date | ||||||||
| 16°F2% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Oct 11 | Oct 18 | Oct 23 | Oct 27 | Oct 31 | Nov 2 | Nov 5 | Nov 9 | Nov 13 |
| 32°F | Oct 26 | Nov 1 | Nov 5 | Nov 10 | Nov 13 | Nov 17 | Nov 21 | Nov 26 | Dec 1 |
| 28°F | Nov 11 | Nov 18 | Nov 23 | Nov 27 | Dec 1 | Dec 5 | Dec 9 | Dec 13 | Dec 21 |
| 24°F84% of yrs | Nov 28 | Dec 3 | Dec 9 | Dec 15 | Dec 19 | Dec 26 | Jan 1 | Jan 10 | Jan 24 |
| 20°F25% of yrs | too rare for a date | ||||||||
| 16°F2% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Grass Valley #2, 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 95949 →Compare Grass Valley with another place →
Weather by month in Grass Valley
July is the warmest month at Grass Valley #2, CA, averaging 88°F by day and 58°F at night; December is the coldest at 53°F and 33°F. A freezing night is all but certain in every month from December to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 74% of years.
Warmth for growing adds up to 3,206 growing degree days a year (base 50°F), fewer than at 80% of the 283 California stations. 30% of them (959) have built up by the end of June, and July adds the most, 716. Precipitation totals 53.2 inches a year, most in December (10.5") and least in July (0.0"); May to September bring 7% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 54 | 33 | 9.3 | 99% | 16 | 7 |
| Feb | 55 | 34 | 9.0 | 98% | 11 | 16 |
| Mar | 58 | 37 | 8.2 | 92% | 7 | 48 |
| Apr | 63 | 40 | 4.4 | 74% | 3 | 108 |
| May | 71 | 47 | 2.5 | 9% | <1 | 287 |
| Jun | 80 | 53 | 0.7 | 0% | 0 | 493 |
| Jul | 88 | 58 | 0.0 | 0% | 0 | 716 |
| Aug | 87 | 57 | 0.1 | 0% | 0 | 685 |
| Sep | 82 | 52 | 0.4 | 0% | 0 | 517 |
| Oct | 72 | 44 | 2.6 | 18% | 1 | 267 |
| Nov | 60 | 37 | 5.5 | 86% | 7 | 59 |
| Dec | 53 | 33 | 10.5 | 99% | 17 | 3 |
Monthly normals 1991–2020 at Grass Valley #2, CA (2,400 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, 9 miles east of Grass Valley, has a last frost 7 days earlier (April 3), a first frost 11 days later (November 24), a season 18 days longer.
When it snows in Grass Valley, California
The first measurable snow (0.1 inch or more) in Grass Valley usually arrives around January 8, and the last of the season around March 5. Those are the middle dates across the winters of 1991–2020 at Grass Valley #2, CA, 5.2 miles away: half of years saw snow earlier, half later. Snow fell in 81% of those winters. The last 32°F night of spring typically comes 36 days after the last snow.
Planting calendar for 95949
| When | What to do |
|---|---|
| January 30 – February 13 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| February 13 – February 27 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| March 13 – March 27 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| April 10 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by August 21 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by October 30 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| November 13 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 95949 is 5 miles from Grass Valley #2, CA, which stands at 2,400 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 95945 (Grass Valley). The 2023 USDA Plant Hardiness Zone Map lists ZIP 95949 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.