Frost dates Wisconsin Madison

Frost dates in Madison, Wisconsin

Last spring frost May 1 First fall frost Oct 9 NOAA 1991-2020

The average last spring frost in Madison is May 1 and the average first fall frost is Oct 9, measured at UW ARBORETUM - MADISON, about 3 miles from the city centre. Below: how sure those dates are, and what to start, sow and set out each week.

Average last spring frostMay 132°F, 50% probability
Average first fall frostOct 932°F, 50% probability
Days between them161average 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%Apr 18Oct 24
50%May 1Oct 9
10%May 17Sep 26

Read it like this: in half of years the last 32°F freeze of spring comes after May 1, and in 1 year in 10 there is still a freeze after May 17. In 1 year in 10 the first fall freeze arrives before Sep 26.

Measured at: UW ARBORETUM - MADISON, WI (NOAA station USC00470273), about 3 miles away at 870 ft, 27 years of record in 1991-2020.

Other stations nearby, for comparison:

  • CHARMANY FARM, WI (NOAA station USC00471416), about 4 miles away at 1,046 ft, 27 years of record in 1991-2020: last spring frost Apr 28, first fall frost Oct 15
  • MADISON DANE RGNL AP, WI (NOAA station USW00014837), about 5 miles away at 866 ft, 29 years of record in 1991-2020: last spring frost May 1, first fall frost Oct 10

Seed-starting schedule for Madison, WI

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

  1. Week of Jan 2314 weeks before last frost
    • Start seeds indoorsLeekJan 23 to Feb 6
    • Start seeds indoorsOnionJan 23 to Feb 6
  2. Week of Jan 3013 weeks before last frost
    • Start seeds indoorsParsleyJan 30 to Feb 6
  3. Week of Feb 612 weeks before last frost
    • Start seeds indoorsCeleryFeb 6 to Feb 20
    • Start seeds indoorsSpinachFeb 6 to Feb 20
  4. Week of Feb 2010 weeks before last frost
    • Start seeds indoorsBroccoliFeb 20 to Mar 6
    • Start seeds indoorsBrussels sproutFeb 20 to Mar 6
    • Start seeds indoorsCabbageFeb 20 to Mar 6
    • Start seeds indoorsKaleFeb 20 to Mar 6
    • Start seeds indoorsKohlrabiFeb 20 to Mar 6
  5. Week of Feb 279 weeks before last frost
    • Start seeds indoorsLettuceFeb 27 to Mar 6
  6. Week of Mar 68 weeks before last frost
    • Start seeds indoorsCauliflowerMar 6 to Mar 20
    • Start seeds indoorsEggplantMar 6 to Mar 20
    • Start seeds indoorsPepperMar 6 to Mar 20
    • Start seeds indoorsSwiss chardMar 6 to Mar 20
  7. Week of Mar 137 weeks before last frost
    • Start seeds indoorsTomatoMar 13 to Mar 27
  8. Week of Mar 206 weeks before last frost
    • Start seeds indoorsBasilMar 20 to Apr 3
    • Set transplants outSpinachMar 20 to Apr 10
  9. Week of Apr 34 weeks before last frost
    • Sow seed outdoorsRadishApr 3 to Apr 17
    • Sow seed outdoorsSwiss chardfrom Apr 3
    • Sow seed outdoorsTurnipApr 3 to Apr 17
    • Set transplants outBroccoliApr 3 to Apr 17
    • Set transplants outBrussels sproutApr 3 to Apr 17
    • Set transplants outCabbagefrom Apr 3
    • Set transplants outKalefrom Apr 3
    • Set transplants outKohlrabifrom Apr 3
    • Set transplants outLeekfrom Apr 3
    • Set transplants outLettuceApr 3 to Apr 10
    • Set transplants outOnionfrom Apr 3
  10. Week of Apr 103 weeks before last frost
    • Start seeds indoorsCucumberApr 10 to Apr 17
    • Set transplants outParsleyApr 10 to Apr 17
  11. Week of Apr 172 weeks before last frost
    • Start seeds indoorsMelonApr 17 to Apr 24
    • Start seeds indoorsPumpkinApr 17 to Apr 24
    • Start seeds indoorsSummer squashApr 17 to Apr 24
    • Start seeds indoorsWinter squashApr 17 to Apr 24
    • Start seeds indoorsZucchiniApr 17 to Apr 24
    • Plant seed potatoes outdoorsPotatoApr 17 to Apr 24
    • Set transplants outCauliflowerfrom Apr 17
    • Set transplants outSwiss chardfrom Apr 17
  12. Week of May 1Last frost week
    • Sow seed outdoorsBeanfrom May 1
    • Sow seed outdoorsParsnipfrom May 1
    • Set transplants outCeleryfrom May 1
  13. Week of May 81 week after last frost
    • Plant slips outdoorsSweet potatoMay 8 to May 15
    • Set transplants outCucumberMay 8 to May 15
    • Set transplants outTomatoMay 8 to May 15
  14. Week of May 152 weeks after last frost
    • Set transplants outBasilfrom May 15
    • Set transplants outEggplantMay 15 to May 22
    • Set transplants outMelonfrom May 15
    • Set transplants outPepperfrom May 15
    • Set transplants outPumpkinfrom May 15
    • Set transplants outSummer squashfrom May 15
    • Set transplants outWinter squashfrom May 15
    • Set transplants outZucchinifrom May 15

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

More in Wisconsin

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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