Merrill, IA 51038 Frost Dates
When can you plant in Merrill, IA?
Around 04/30 is the usual last spring frost, about 245 days away. The first fall frost typically arrives around 10/04, about 157 frost-free days later.
Merrill sits in USDA Zone 5a (-20 to -15°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
What to do before the first frost
About 5 weeks of growing season left in Merrill before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 04/30 isn't a guarantee
04/30 is the middle of 30 years of NOAA records, not a promise. Plant by 04/17 and you're betting against frost in roughly 9 years out of 10. 05/12 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Merrill compares
About 157 days separate Merrill's last and first frost, putting it 33,408 of 40,283 ZIP codes nationally. Within IA, it ranks 845 of 1,042.
Learn more
zone vs. frost date covers why Zone 5a and Merrill's frost date answer different questions. the frost range covers how to read the range around Merrill's dates instead of trusting one.