Ontario, CA Frost Dates
The last spring frost in Ontario usually comes around January 4 and the first fall frost around December 30.
| Spring (last) | Fall (first) | |
|---|---|---|
| Frost, 32°F | January 4 | December 30 |
| Hard freeze, 28°F | Rare | Rare |
Growing season: about 365 days.
Frequently asked questions
When is the last frost in Ontario, CA?
The median date of the last spring frost (32°F) is January 4. In half of years the last frost comes earlier and in half it comes later, so waiting a week or two past January 4 lowers the risk for tender plants.
When is the first frost in Ontario?
The median date of the first fall frost (32°F) is December 30.
How long is the growing season in Ontario?
About 365 days between the median last spring frost and first fall frost.
NOAA NCEI U.S. Climate Normals 1991-2020, station USW00003102. Median (50% probability) dates. Low spots and valleys can frost later in spring and earlier in fall than the station.