St. Marys, KS 66536 Frost Dates
When can you plant in St. Marys, KS?
Around 04/18 is the usual last spring frost, about 233 days away. The first fall frost typically arrives around 10/19, about 183 frost-free days later.
Zone 6b (-5 to 0°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 St. Marys, not a forecast for this year.
What to do before the first frost
About 7 weeks of growing season left in St. Marys 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
04/18 is the middle of 30 years of NOAA records, not a promise. Plant by 04/04 and you're betting against frost in roughly 9 years out of 10. 05/02 is the safer bet, historically only a 1-in-10 chance of frost that late.
How St. Marys compares
St. Marys's growing season runs about 183 days, ranking 23,869 of 40,283 US ZIP codes measured here, longest to shortest. Within KS, it ranks 438 of 745.
Learn more
local microclimates covers what one yard in St. Marys can differ from the 66536 normal. zone vs. frost date covers why Zone 6b and St. Marys's frost date answer different questions.