Frost dates for Fontana, California
Fontana doesn't get a freezing night every winter: about 41 years in 100 have one. In those years, half have had their last frost by January 4 and half their first by December 30.
Frost dates for
Fontana, California
Last spring frost
January 4
Not every winter has one: about 41 years in 100 have a freezing night here. In those years, half have their last frost by this date, and 1 in 10 still have one after February 7.
First fall frost
December 30
In years with a freeze, half have their first one by this date, and 1 in 10 by December 11.
Growing season
All year
In a typical year there is no freezing night at all. 9 years in 10 get at least 339 frost-free days in a row.
Hardiness zone
10a
2023 USDA map: the coldest night of winter averages 30°F to 35°F. It was 10a on the 2012 map too. ZIP codes within about 6 miles of the city's center: 1 in 8a and 8 in 10a.
Print a year planner for Fontana
Frost risk through the year
How sure are these dates?
A frost date is a probability, not a promise. NOAA worked out, from 30 years of nightly lows, how often the last spring frost and the first fall frost fall on each date. The middle column is the typical year. The outer columns are the early and late years that come about once a decade.
| Early year 1 in 10 | Typical year 1 in 2 | Late year 1 in 10 | |
|---|---|---|---|
| Last frost in spring | December 14 | January 4 | February 7 |
| First frost in fall | December 11 | December 30 | February 1 |
In a typical year there is no freezing night at all. In 1 year in 10, the longest frost-free stretch is 339 days or shorter.
- Frost possible (36°F at the station): about 93 years in 100 have one. In those years the last typically comes on January 27 and the first on December 17. On clear, still nights the ground can be several degrees colder than the thermometer, so frost can form on plants when the official reading is in the mid-30s.
Planting calendar for Fontana
These dates count from the typical last and first frosts, using the planting rules published by Colorado State University Extension (spring), Virginia Cooperative Extension (fall crops) and University of Minnesota Extension (garlic, where winters are hard). Weather in any one year can run early or late, so check the forecast before you plant tender crops.
Frost comes in fewer than half of years here (about 41 years in 100), so we don't build a planting calendar around it: in most years there is no last frost to plant after. Your county's extension office publishes planting dates made for your climate.
For spring bulbs such as tulips and daffodils, plant once the soil has cooled to about 50 to 55°F and keep going until a couple of weeks before the ground freezes. Our guide to fall planting explains how to tell.
Where these numbers come from
These dates come from NOAA's weather station Ontario International Airport (station USW00003102), 9 miles from the center of Fontana. It sits 360 feet lower, at 950 feet above sea level. NOAA rates this station's record as representative: at least 10 of the 30 years, with the gaps filled from nearby stations.
The same station also gives the frost dates for Ontario, Rancho Cucamonga, Pomona, Upland, Chino Hills, Diamond Bar, Montclair and Claremont.
Our ZIP code lookup matches these 9 ZIP codes to the same station, so they get the same dates: 91730, 91737, 91739, 91761, 91762, 91764, 92335, 92337, 92358. Hardiness zones are worked out separately for each ZIP code.
Nearby places
- San Bernardino, California: frost not every year (10 miles away)
- Riverside, California: frost not every year (15 miles away)
- Victorville, California: last frost around March 18, first frost around November 11 (30 miles away)
See frost dates across California, or look up your own ZIP code for the station nearest you. Want the background? Read what a last frost date really means.