St. Louis, MO 63103 Frost Dates
St. Louis, MO: when does the frost end?
Typically, the last spring freeze lands around 04/01, roughly 216 days out. Fall's first freeze usually shows up around 11/04, roughly 218 days after the last spring frost.
Zone 7a (0 to 5°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. Louis, not a forecast for this year.
Stretching the season past the first frost
With roughly 10 weeks until St. Louis's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
How much risk comes with planting early here
04/01 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/14 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 04/18 and only about 1 year in 10 sees frost after that.
St. Louis against the rest of the dataset
St. Louis's growing season runs about 218 days, ranking 13,143 of 40,283 US ZIP codes measured here, longest to shortest. Within MO, it ranks 47 of 1,129.
Learn more
Before leaning on 63103's figures: local microclimates explains what one yard in St. Louis can differ from the 63103 normal, while zone vs. frost date explains why Zone 7a and St. Louis's frost date answer different questions.