Oslo, MN 56744 Frost Dates
When can you plant in Oslo, MN?
Typically, the last spring freeze lands around 05/15, roughly 260 days out. The first fall frost typically arrives around 09/26, about 134 frost-free days later.
Zone 4a (-30 to -25°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 Oslo, not a forecast for this year.
What to do before the first frost
About 4 weeks of growing season left in Oslo before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 05/15 isn't a guarantee
05/15 is the middle of 30 years of NOAA records, not a promise. Plant by 05/01 and you're betting against frost in roughly 9 years out of 10. 05/28 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Oslo compares
At roughly 134 frost-free days, Oslo places 38,024 of 40,283 ZIP codes in this dataset. Within MN, it ranks 819 of 943.
Learn more
local microclimates covers what one yard in Oslo can differ from the 56744 normal. zone vs. frost date covers why Zone 4a and Oslo's frost date answer different questions.