Upland, CA 91784 Frost Dates
91784, near Upland, CA: the frost window
Typically, the last spring freeze lands around 01/04, roughly 129 days out. Fall's first freeze usually shows up around 12/30, roughly 365 days after the last spring frost.
The USDA Plant Hardiness Zone Map puts Upland in Zone 10a (30 to 35°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
Stretching the season past the first frost
Upland's growing season runs out in roughly 18 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
Why 01/04 isn't a guarantee
01/04 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 02/07 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 12/14 and only about 1 year in 10 sees frost after that.
Upland against the rest of the dataset
At roughly 365 frost-free days, Upland places 682 of 40,283 ZIP codes in this dataset. Within CA, it ranks 299 of 2,555.
Learn more
Two guides worth reading on 91784: local microclimates, on what one yard in Upland can differ from the 91784 normal, and zone vs. frost date, on why Zone 10a and Upland's frost date answer different questions.