Monrovia, CA 91016 Frost Dates
Frost dates for Monrovia, CA, ZIP 91016
The last spring frost here typically falls around 01/04, about 129 days from today. The first fall frost typically arrives around 01/02, about 365 frost-free days later.
The USDA Plant Hardiness Zone Map puts Monrovia in Zone 10a (30 to 35°F average annual minimum); frost dates are NOAA's 1991-2020 station normal, not this year's forecast.
What to do before the first frost
Zone 10a around Monrovia has about 18 weeks left before the first fall frost — that's the usual window to get a cold frame up if you want to keep harvesting past it.
Why 01/04 isn't a guarantee
01/04 is the middle of 30 years of NOAA records, not a promise. Plant by 01/28 and you're betting against frost in roughly 9 years out of 10. 12/19 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Monrovia compares
Monrovia's growing season runs about 365 days, ranking 990 of 40,283 US ZIP codes measured here, longest to shortest. Within CA, it ranks 417 of 2,555.
Learn more
zone vs. frost date explains why Zone 10a and Monrovia's frost date answer different questions, and the frost range explains how to read the range around Monrovia's dates instead of trusting one.