Frost dates Missouri St. Louis

Frost dates in St. Louis, Missouri

Last spring frost Apr 1 First fall frost Nov 4 NOAA 1991-2020

The average last spring frost in St. Louis is Apr 1 and the average first fall frost is Nov 4, measured at ST LOUIS SCI CTR, about 4 miles from the city centre. Below: how sure those dates are, and what to start, sow and set out each week.

Average last spring frostApr 132°F, 50% probability
Average first fall frostNov 432°F, 50% probability
Days between them217average frost-free season
How sure is that date? NOAA probability levels for a 32°F freeze
ProbabilityFreeze still comes after (spring)First freeze has come by (fall)
90%Mar 14Nov 21
50%Apr 1Nov 4
10%Apr 18Oct 24

Read it like this: in half of years the last 32°F freeze of spring comes after Apr 1, and in 1 year in 10 there is still a freeze after Apr 18. In 1 year in 10 the first fall freeze arrives before Oct 24.

Measured at: ST LOUIS SCI CTR, MO (NOAA station USC00237452), about 4 miles away at 515 ft, 25 years of record in 1991-2020.

Other stations nearby, for comparison:

  • CAHOKIA, IL (NOAA station USC00111160), about 4 miles away at 400 ft, 20 years of record in 1991-2020: last spring frost Apr 6, first fall frost Oct 27
  • CAHOKIA ST LOUIS AP, IL (NOAA station USW00003960), about 4 miles away at 413 ft, 20 years of record in 1991-2020: last spring frost Apr 8, first fall frost Oct 26

Seed-starting schedule for St. Louis, MO

Counted from a last frost date of Apr 1 (the average: a freeze comes later than this in half of years).

  1. Week of Dec 2414 weeks before last frost
    • Start seeds indoorsLeekDec 24 to Jan 7
    • Start seeds indoorsOnionDec 24 to Jan 7
  2. Week of Dec 3113 weeks before last frost
    • Start seeds indoorsParsleyDec 31 to Jan 7
  3. Week of Jan 712 weeks before last frost
    • Start seeds indoorsCeleryJan 7 to Jan 21
    • Start seeds indoorsSpinachJan 7 to Jan 21
  4. Week of Jan 2110 weeks before last frost
    • Start seeds indoorsBroccoliJan 21 to Feb 4
    • Start seeds indoorsBrussels sproutJan 21 to Feb 4
    • Start seeds indoorsCabbageJan 21 to Feb 4
    • Start seeds indoorsKaleJan 21 to Feb 4
    • Start seeds indoorsKohlrabiJan 21 to Feb 4
  5. Week of Jan 289 weeks before last frost
    • Start seeds indoorsLettuceJan 28 to Feb 4
  6. Week of Feb 48 weeks before last frost
    • Start seeds indoorsCauliflowerFeb 4 to Feb 18
    • Start seeds indoorsEggplantFeb 4 to Feb 18
    • Start seeds indoorsPepperFeb 4 to Feb 18
    • Start seeds indoorsSwiss chardFeb 4 to Feb 18
  7. Week of Feb 117 weeks before last frost
    • Start seeds indoorsTomatoFeb 11 to Feb 25
  8. Week of Feb 186 weeks before last frost
    • Start seeds indoorsBasilFeb 18 to Mar 4
    • Set transplants outSpinachFeb 18 to Mar 11
  9. Week of Mar 44 weeks before last frost
    • Sow seed outdoorsRadishMar 4 to Mar 18
    • Sow seed outdoorsSwiss chardfrom Mar 4
    • Sow seed outdoorsTurnipMar 4 to Mar 18
    • Set transplants outBroccoliMar 4 to Mar 18
    • Set transplants outBrussels sproutMar 4 to Mar 18
    • Set transplants outCabbagefrom Mar 4
    • Set transplants outKalefrom Mar 4
    • Set transplants outKohlrabifrom Mar 4
    • Set transplants outLeekfrom Mar 4
    • Set transplants outLettuceMar 4 to Mar 11
    • Set transplants outOnionfrom Mar 4
  10. Week of Mar 113 weeks before last frost
    • Start seeds indoorsCucumberMar 11 to Mar 18
    • Set transplants outParsleyMar 11 to Mar 18
  11. Week of Mar 182 weeks before last frost
    • Start seeds indoorsMelonMar 18 to Mar 25
    • Start seeds indoorsPumpkinMar 18 to Mar 25
    • Start seeds indoorsSummer squashMar 18 to Mar 25
    • Start seeds indoorsWinter squashMar 18 to Mar 25
    • Start seeds indoorsZucchiniMar 18 to Mar 25
    • Plant seed potatoes outdoorsPotatoMar 18 to Mar 25
    • Set transplants outCauliflowerfrom Mar 18
    • Set transplants outSwiss chardfrom Mar 18
  12. Week of Apr 1Last frost week
    • Sow seed outdoorsBeanfrom Apr 1
    • Sow seed outdoorsParsnipfrom Apr 1
    • Set transplants outCeleryfrom Apr 1
  13. Week of Apr 81 week after last frost
    • Plant slips outdoorsSweet potatoApr 8 to Apr 15
    • Set transplants outCucumberApr 8 to Apr 15
    • Set transplants outTomatoApr 8 to Apr 15
  14. Week of Apr 152 weeks after last frost
    • Set transplants outBasilfrom Apr 15
    • Set transplants outEggplantApr 15 to Apr 22
    • Set transplants outMelonfrom Apr 15
    • Set transplants outPepperfrom Apr 15
    • Set transplants outPumpkinfrom Apr 15
    • Set transplants outSummer squashfrom Apr 15
    • Set transplants outWinter squashfrom Apr 15
    • Set transplants outZucchinifrom Apr 15

Not in the city centre? Look up your own ZIP code

More in Missouri

Where the numbers come from

Sources and method

Frost dates. U.S. Climate Normals 2020: U.S. Annual/Seasonal Climate Normals (1991-2020), NOAA National Centers for Environmental Information (Palecki, Durre, Applequist, Arguez and Lawrimore, 2021). These are 30-year station statistics for 1991 to 2020. "Frost" here means an air temperature of 32°F or lower at the station. We use 6,539 stations that have at least 10 years of record and a published date; 176 more are stations where a freeze is too rare for NOAA to date, and 180 are stations cold enough to have frost risk all year.

Probability level. The headline dates are NOAA's 50% level: in half of years the last spring freeze comes later than that date, and in half of years the first fall freeze comes earlier. The 10% and 90% levels are shown next to them. For tender plants, the 10% spring date is the safer one to plan from: a freeze follows it in only 1 year in 10.

Which station. Your ZIP code is matched to the nearest of those stations by straight-line distance from the ZIP code's centre point (GeoNames, geonames.org, CC BY 4.0; 40,979 ZIP codes in the 50 states and DC). Nearest is not always most alike: a station on a hill, in a valley or by the water can differ from your garden by a week or more. That is why the station's name, distance and elevation are shown with every result, along with two more stations nearby. NOAA makes the same point: the normals are limited between stations as distance grows horizontally and vertically.

Seed-starting offsets. Growing Vegetables: When to Plant Your Vegetable Garden, a fact sheet from University of New Hampshire Extension. It gives each crop's weeks from seed to transplant and when it is safe to set out or sow relative to the last frost. The method is theirs too: take the planting date and count back the seed-to-transplant weeks. Where the fact sheet gives a range of planting dates, the start-indoors dates count back from the earliest one. The figures used, as the fact sheet states them:

  • Basil: Seed to transplant 6-8 weeks; set out 2 weeks after last frost.
  • Bean: Plant seed in garden after last frost.
  • Broccoli: Seed to transplant 4-6 weeks; set out 2-4 weeks before last frost.
  • Brussels sprout: Seed to transplant 4-6 weeks; set out 2-4 weeks before last frost.
  • Cabbage: Seed to transplant 4-6 weeks; set out 4 weeks before last frost.
  • Cauliflower: Seed to transplant 4-6 weeks; set out 2 weeks before last frost.
  • Celery: Seed to transplant 10-12 weeks; set out after last frost.
  • Cucumber: Seed to transplant 3-4 weeks; set out 1-2 weeks after last frost.
  • Eggplant: Seed to transplant 8-10 weeks; set out 2-3 weeks after last frost.
  • Kale: Seed to transplant 4-6 weeks; set out 4 weeks before last frost.
  • Kohlrabi: Seed to transplant 4-6 weeks; set out 4 weeks before last frost.
  • Leek: Seed to transplant 8-10 weeks; set out 4 weeks before last frost.
  • Lettuce: Seed to transplant 4-5 weeks; set out 3-4 weeks before last frost.
  • Melon: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.
  • Onion: Seed to transplant 8-10 weeks; set out 4 weeks before last frost.
  • Parsley: Seed to transplant 9-10 weeks; set out 2-3 weeks before last frost.
  • Parsnip: Plant seed in garden after last frost.
  • Pepper: Seed to transplant 8-10 weeks; set out 2 weeks after last frost.
  • Potato: Plant seed potatoes in garden 1-2 weeks before last frost.
  • Pumpkin: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.
  • Radish: Plant seed in garden 2-4 weeks before last frost.
  • Spinach: Seed to transplant 4-6 weeks; set out 3-6 weeks before last frost.
  • Summer squash: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.
  • Sweet potato: Plant slips in garden 1-2 weeks after last frost.
  • Swiss chard: Seed to transplant 4-6 weeks; set out 2 weeks before last frost; or plant seed in garden 4 weeks before last frost.
  • Tomato: Seed to transplant 6-8 weeks; set out 1-2 weeks after last frost.
  • Turnip: Plant seed in garden 2-4 weeks before last frost.
  • Winter squash: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.
  • Zucchini: Seed to transplant 3-4 weeks; set out 2 weeks after last frost.

Not on the calendar. The same fact sheet times these by soil temperature, not by frost date, so they get no date here:

  • Pea: as soon as the soil thaws.
  • Beet: when the soil warms to 45°F.
  • Carrot: when the soil warms to 60°F.
  • Corn: when the soil warms to 60°F.
  • Cucumber, pumpkin, summer squash, winter squash, zucchini: direct-sow when the soil warms to 70°F.

Rutabaga is left out: the fact sheet gives it New Hampshire calendar dates, not a frost offset.

The fact sheet was written for New Hampshire. The offsets are relative to the last frost, so they carry to other places with a spring frost, but where winters are mild many cool-season crops are grown in fall and winter instead. Your state's extension service has the local calendar. Dates are 30-year statistics, not a forecast: check the forecast before setting tender plants out.

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