USDA Hardiness Zone 10a
Frost Dates for 91306 — Winnetka, California
NOAA 1991–2020 normals from Woodland Hills Pierce College, CA (790 ft), 2 miles south.
Updated
In Winnetka, the last spring frost (32°F) is around January 24 in half of years and has passed by March 5 in nine years out of ten. The first fall frost comes around December 15, as early as November 27 one year in ten, leaving a typical freeze-free season of 329 days (NOAA, Woodland Hills Pierce College, CA).
- Last spring frost
- January 24
- First fall frost
- December 15
- Growing season
- 329 days
- Hardiness zone
- 10a
50% probability
50% probability
freeze-free, 50%
30 to 35°F (-1.1 to 1.7°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 Winnetka
Half of springs at Woodland Hills Pierce College, CA see their last 32°F night by January 24; only one in ten is past it by December 21, and one in ten still has one after March 5. Planting tender crops after February 12 leaves a 30% risk of a frost on them, after February 23 20%, and after March 5 10%. The 40 days between the even-odds date and the one-in-ten date is wider than at 85% 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 15 in half of years, as early as November 27 one year in ten, and holds off past January 26 one year in ten. A hard freeze of 28°F is less common: it came in 35% of winters. The freeze-free season lasts 329 days in a typical year, longer than at 81% of the 219 California stations; it reaches 365 days one year in ten and falls short of 277 one year in ten. On average 11 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 March 2, and return around November 29. A 24°F night is unusual: 5% of winters had one.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jan 30 | Feb 14 | Feb 21 | Feb 27 | Mar 2 | Mar 8 | Mar 15 | Mar 28 | Apr 7 |
| 32°F91% of yrs | Dec 21 | Dec 31 | Jan 6 | Jan 15 | Jan 24 | Feb 3 | Feb 12 | Feb 23 | Mar 5 |
| 28°F35% of yrs | too rare for a date | ||||||||
| 24°F5% of yrs | too rare for a date | ||||||||
| 20°F0% of yrs | too rare for a date | ||||||||
| Low | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Nov 12 | Nov 18 | Nov 23 | Nov 26 | Nov 29 | Dec 2 | Dec 6 | Dec 11 | Dec 19 |
| 32°F91% of yrs | Nov 27 | Dec 2 | Dec 6 | Dec 11 | Dec 15 | Dec 22 | Dec 28 | Jan 4 | Jan 26 |
| 28°F35% of yrs | too rare for a date | ||||||||
| 24°F5% of yrs | too rare for a date | ||||||||
| 20°F0% of yrs | too rare for a date | ||||||||
Freeze probabilities 1991–2020 at Woodland Hills Pierce 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 91306 →Compare Winnetka with another place →
Weather by month in Winnetka
August is the warmest month at Woodland Hills Pierce College, CA, averaging 97°F by day and 61°F at night; December is the coldest at 69°F and 42°F. From April to October the chance of a 32°F night stays under 10% each month. In spring, February still brings one in 31% of years and March still brings one in 10% of years.
Warmth for growing adds up to 6,002 growing degree days a year (base 50°F), more than at 90% of the 283 California stations. 39% of them (2,335) have built up by the end of June, and August adds the most, 902. Precipitation totals 16.5 inches a year, most in February (4.6") and least in July (0.0"); May to September bring 4% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 70 | 43 | 3.7 | 53% | 3 | 211 |
| Feb | 70 | 44 | 4.6 | 31% | 2 | 201 |
| Mar | 74 | 46 | 2.7 | 10% | 1 | 312 |
| Apr | 78 | 48 | 0.8 | 2% | <1 | 393 |
| May | 82 | 53 | 0.4 | 0% | 0 | 536 |
| Jun | 89 | 57 | 0.1 | 0% | 0 | 681 |
| Jul | 95 | 61 | 0.0 | 0% | 0 | 866 |
| Aug | 97 | 61 | 0.0 | 0% | 0 | 902 |
| Sep | 94 | 59 | 0.1 | 0% | 0 | 786 |
| Oct | 85 | 53 | 0.6 | 0% | 0 | 591 |
| Nov | 76 | 46 | 0.8 | 15% | 1 | 339 |
| Dec | 69 | 42 | 2.7 | 63% | 4 | 184 |
Monthly normals 1991–2020 at Woodland Hills Pierce College, CA (790 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, Northridge Cal State, CA, 4 miles northeast of Winnetka, has a 32°F night in 18% of winters against 91% here, and a coolest-month low 4°F warmer (46°F).
When it snows in Winnetka, California
Measurable snow is rare here: only 0 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Woodland Hills Pierce College, CA, 1.9 miles away, so there is no typical first-snow date to plan around.
Planting calendar for 91306
| When | What to do |
|---|---|
| November 15 – November 29 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| November 29 – December 13 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| December 27 – January 10 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| January 24 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by September 22 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by December 1 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| December 15 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 91306 is 2 miles from Woodland Hills Pierce College, CA, which stands at 790 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 14 other ZIP codes share the station; its figures are presented in full for 91335 (Reseda). The 2023 USDA Plant Hardiness Zone Map lists ZIP 91306 in zone 10a, the band where the coldest night of the year averaged 30 to 35°F (-1.1 to 1.7°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.