Merrimac, WI 53561 Frost Dates
When can you plant in Merrimac, WI?
Typically, the last spring freeze lands around 05/05, roughly 250 days out. The first fall frost typically arrives around 10/05, about 152 frost-free days later.
Zone 5a (-20 to -15°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 Merrimac, not a forecast for this year.
What to do before the first frost
About 5 weeks of growing season left in Merrimac 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
05/05 is the middle of 30 years of NOAA records, not a promise. Plant by 04/21 and you're betting against frost in roughly 9 years out of 10. 05/21 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Merrimac compares
At roughly 152 frost-free days, Merrimac places 34,854 of 40,283 ZIP codes in this dataset. Within WI, it ranks 527 of 860.
Learn more
local microclimates covers what one yard in Merrimac can differ from the 53561 normal. zone vs. frost date covers why Zone 5a and Merrimac's frost date answer different questions.