Dayton, WY 59089 Frost Dates
Frost dates for Dayton, WY, ZIP 59089
Around 05/21 is the usual last spring frost, about 266 days away. The first fall frost typically arrives around 09/17, about 117 frost-free days later.
Zone 4b (-25 to -20°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 Dayton, not a forecast for this year.
What to do before the first frost
Zone 4b around Dayton has about 3 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.
The actual range around Dayton's last frost
05/21 is the middle of 30 years of NOAA records, not a promise. Plant by 05/09 and you're betting against frost in roughly 9 years out of 10. 06/02 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Dayton compares
Dayton's growing season runs about 117 days, ranking 39,252 of 40,283 US ZIP codes measured here, longest to shortest. Within WY, it ranks 113 of 192.
Learn more
zone vs. frost date explains why Zone 4b and Dayton's frost date answer different questions, and the frost range explains how to read the range around Dayton's dates instead of trusting one.