Spencer, ID 83446 Frost Dates
Frost dates for Spencer, ID, ZIP 83446
The last spring frost here typically falls around 05/18, about 263 days from today. The first fall frost typically arrives around 09/30, about 132 frost-free days later.
The USDA Plant Hardiness Zone Map puts Spencer in Zone 5b (-15 to -10°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 5b around Spencer has about 5 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 05/18 isn't a guarantee
05/18 is the middle of 30 years of NOAA records, not a promise. Plant by 05/03 and you're betting against frost in roughly 9 years out of 10. 06/09 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Spencer compares
Spencer's growing season runs about 132 days, ranking 38,244 of 40,283 US ZIP codes measured here, longest to shortest. Within ID, it ranks 171 of 320.
Learn more
zone vs. frost date explains why Zone 5b and Spencer's frost date answer different questions, and the frost range explains how to read the range around Spencer's dates instead of trusting one.