Last frost date in Ontario, California
January 4
Average last frost in spring. In an early year (1 in 10) it's over by December 14; in a late year (1 in 10) it comes after February 7.
December 30
Average first frost in fall. 1 year in 10 it comes by December 11.
A 32°F night happens here about 4 years in 10; in those years these are the usual dates.
Source: NOAA U.S. Climate Normals 1991–2020, station Ontario International AP (USW00003102), 1.3 miles from Ontario, elevation 949 ft. NOAA National Centers for Environmental Information. These are long-term averages, not a forecast.
| Early year | Average | Late year | |
|---|---|---|---|
| Last frost in spring | Dec 14 | Jan 4 | Feb 7 |
| First frost in fall | Dec 11 | Dec 30 | Feb 1 |
An early or late year is one in 10: 1 year in 10 the frost comes before the early date, and 1 year in 10 after the late date.
Frost-free days in an average year: 365
Planting calendar for Ontario
Fall planting
USDA dates for places whose average first freeze is about December 20 (Ontario: December 30).
- SoybeansJune 1 – July 30 (past for this year)
- Summer squashJune 1 – Oct 1 (past for this year)
- Sweet potatoesJune 1 – July 1 (past for this year)
- Swiss chardJune 1 – Dec 31Now
- Black-eyed peasJuly 1 – Sept 20 (past for this year)
- Eggplant plantsAug 1 – Sept 30 (past for this year)
- OkraAug 1 – Oct 1 (past for this year)
- PotatoesAug 1 – Sept 15 (past for this year)
- Winter squashAug 1 – Sept 1 (past for this year)
- CucumbersAug 15 – Oct 1 (past for this year)
- Peppers plantsAug 15 – Oct 1 (past for this year)
- Witloof chicoryAug 15 – Oct 15 (past for this year)
- BeetsSept 1 – Dec 31Now
- Broccoli plantsSept 1 – Dec 31Now
- Brussels sprouts plantsSept 1 – Dec 31Now
- Cabbage plantsSept 1 – Dec 31Now
- Chinese cabbageSept 1 – Dec 1Now
- Collards plantsSept 1 – Dec 31Now
- EndiveSept 1 – Dec 31Now
- Florence fennelSept 1 – Dec 1Now
- KaleSept 1 – Dec 31Now
- KohlrabiSept 1 – Dec 31Now
- Lima beansSept 1 – Oct 1 (past for this year)
- ParsleySept 1 – Dec 31Now
- ParsnipsSept 1 – Dec 1Now
- SalsifySept 1 – Oct 31Now
- Snap beansSept 1 – Nov 1Now
- SorrelSept 1 – Dec 31Now
- TomatoesSept 1 – Nov 1Now
- CarrotsSept 15 – Dec 1Now
- Cauliflower plantsSept 15 – Nov 1Now
- GarlicSept 15 – Nov 15Now
- Head lettuce plantsSept 15 – Dec 31Now
- Leaf lettuceSept 15 – Dec 31Now
- LeeksSept 15 – Nov 1Now
- Mustard greensSept 15 – Dec 1Now
- Onion seedSept 15 – Nov 1Now
- ShallotsSept 15 – Nov 1Now
- Celery and celeriac plantsOct 1 – Dec 31Now
- Corn saladOct 1 – Dec 31Now
- DandelionOct 1 – Dec 31Now
- Garden peasOct 1 – Dec 31Now
- Onion plants plantsOct 1 – Dec 31Now
- RadishesOct 1 – Dec 31Now
- SpinachOct 1 – Dec 31Now
- TurnipsOct 1 – Dec 31Now
- Upland cressOct 1 – Dec 31Now
- RutabagaOct 15 – Nov 15Now
- Chervil and chivesNov 1 – Dec 31Soon
- Onion setsNov 1 – Dec 31Soon
USDA lists horseradish as generally spring-planted here.
Spring planting
Ontario's average last frost falls outside the dates USDA's planting table covers, so we don't give spring planting dates here.
Planting dates: USDA Home and Garden Bulletin No. 9 (1967), “Suburban and Farm Vegetable Gardens,” tables 4 and 5 (earliest safe spring and latest safe fall dates), applied to this place's NOAA frost dates. “Plants” means setting out transplants, not sowing seed. How we match the table.
Nearby in California
- Chino 5 mi · last frost Jan 17
- Eastvale 5 mi · last frost Jan 17
- Montclair 6 mi · last frost Jan 8
- Upland 6 mi · last frost Jan 4
- Rancho Cucamonga 7 mi · last frost Jan 4