It's growing season in Fontana, CA

Fontana's average last spring frost is around Jan 4, and its first fall frost around Dec 30 — a growing season of roughly 360 days. These figures come from the nearest NOAA station with long-term records (Ontario Intl Ap, CA).

These are 1991–2020 averages, not guarantees: about half of years see a frost a little later in spring or earlier in fall. Cautious gardeners wait a week or two past the last-frost date before setting out frost-tender plants, or keep row cover handy for surprise cold snaps.

To build a planting calendar, count backward from the last spring frost for indoor seed-starting, and forward from the first fall frost for crops that need time to mature before cold returns.