Sully, IA 50251 Frost Dates
When can you plant in Sully, IA?
Around 05/03 is the usual last spring frost, about 248 days away. The first fall frost typically arrives around 10/06, about 155 frost-free days later.
The USDA Plant Hardiness Zone Map puts Sully 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
About 6 weeks of growing season left in Sully before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
How much risk comes with planting early here
05/03 is the middle of 30 years of NOAA records, not a promise. Plant by 04/19 and you're betting against frost in roughly 9 years out of 10. 05/17 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Sully compares
Sully's growing season runs about 155 days, ranking 34,046 of 40,283 US ZIP codes measured here, longest to shortest. Within IA, it ranks 873 of 1,042.
Learn more
the frost range covers how to read the range around Sully's dates instead of trusting one. local microclimates covers what one yard in Sully can differ from the 50251 normal.