Flagstaff, AZ 86001 Frost Dates
Frost dates for Flagstaff, AZ, ZIP 86001
Around 06/11 is the usual last spring frost, about 287 days away. The first fall frost typically arrives around 09/25, about 99 frost-free days later.
Zone 6a (-10 to -5°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 Flagstaff, not a forecast for this year.
What to do before the first frost
Zone 6a around Flagstaff has about 4 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 06/11 isn't a guarantee
06/11 is the middle of 30 years of NOAA records, not a promise. Plant by 05/26 and you're betting against frost in roughly 9 years out of 10. 06/30 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Flagstaff compares
About 99 days separate Flagstaff's last and first frost, putting it 39,728 of 40,283 ZIP codes nationally. Within AZ, it ranks 500 of 506.
Learn more
the frost range explains how to read the range around Flagstaff's dates instead of trusting one, and local microclimates explains what one yard in Flagstaff can differ from the 86001 normal.