Glendora, CA 91740 Frost Dates
91740, near Glendora, CA: the frost window
The last spring frost here typically falls around 01/08, about 133 days from today. Fall's first freeze usually shows up around 12/28, roughly 354 days after the last spring frost.
Zone 10a (30 to 35°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Glendora, not a forecast for this year.
Stretching the season past the first frost
Glendora's growing season runs out in roughly 17 weeks — a cold frame or greenhouse kit is the usual way to keep cool-weather crops going past the first frost.
How much risk comes with planting early here
01/08 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 02/18 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.
Glendora against the rest of the dataset
Glendora's growing season runs about 354 days, ranking 2,169 of 40,283 US ZIP codes measured here, longest to shortest. Within CA, it ranks 973 of 2,555.
Learn more
Two guides worth reading on 91740: zone vs. frost date, on why Zone 10a and Glendora's frost date answer different questions, and the frost range, on how to read the range around Glendora's dates instead of trusting one.