Seed Starting Calendar for South Dakota

Q: When should I start seeds indoors in South Dakota?

Count back from the median last frost where you garden. At Rapid City (Rapid City) that date is May 3, so for spring 2027 onions start indoors Jan 25 to Feb 8, peppers Mar 8 to Mar 22 and tomatoes Mar 15 to Mar 29. Across South Dakota's 158 NOAA stations the median last frost runs from May 1 to May 18 for the middle 90 percent, so a garden near Hill City starts later than one near Mitchell.

Q: When is the last frost in South Dakota?

It depends on the station. The earliest median last spring freeze in South Dakota is April 27 at Mitchell; the latest is June 1 at Hill City. A median is a coin flip: at Rapid City the last 32°F freeze comes after May 3 in half of years, and has passed by May 17 in 9 of 10 years (NOAA 1991 to 2020 normals).

Q: When can I plant tomatoes outside in South Dakota?

UNH Extension sets tomatoes out 1 to 2 weeks after the last frost, which at Rapid City is May 10 to May 17 in 2027. Tomatoes are frost tender, so the date to watch is May 17, when 9 of 10 springs at Rapid City have had their last 32°F night. Hardening off starts two weeks before setting out (Apr 26 to May 10).

Q: What months do I plant vegetables in South Dakota?

SDSU Extension publishes planting months by region (South Dakota). For South Dakota, tomatoes go in during May and June. Seeds for transplants go in 4 to 10 weeks ahead of those months, depending on the crop.

Q: What does SDSU Extension say about planting dates in South Dakota?

SDSU Extension's Vegetable Gardening in South Dakota puts it this way: "Comparing the maps with the table below can help you determine planting dates, as well as the average length of the growing season in your area." The guide is linked below with the date it was read (September 21, 2026).

Q: How many weeks before the last frost do I start peppers and eggplant?

UNH Extension gives 8 to 10 weeks from seed to transplant for both, and sets peppers out 2 weeks after the last frost and eggplant 2 to 3 weeks after, so the sowing date is 6 to 8 weeks before the median last frost. At Rapid City that is Mar 8 to Mar 22 for peppers.

Q: How long do seedlings need to harden off?

About two weeks. University of Missouri Extension: "Hardening should be started about two weeks before planting in the garden." University of Minnesota Extension adds that seedlings should go out on a cloudy day or in the late afternoon.

Median last frost from May 1 to May 18 across South Dakota

NOAA stations

158

Median last frost, Rapid City

May 3

Passed in 9 of 10 years

May 17

Last frost

Last spring frost dates in South Dakota

Sioux Falls and Winner reach a median last frost around May 1, Rapid City below the Black Hills around May 3, and Aberdeen and Buffalo around May 9 to May 10.

Three dates per station from the NOAA 1991 to 2020 normals. The median is the date half of springs run past. The last column is the date the last 32°F night has passed by in 9 years out of 10, the one to hold tender transplants for.

Station	Elevation	Early (1 in 10 years later than this)	Median last frost	Passed in 9 of 10 years	Median first fall frost
Sioux FallsSioux Falls, USW00014944	1,430 ft	Apr 18	May 1	May 14	Oct 6
Winner Wiley FieldWinner Wiley Field, USW00094990	2,032 ft	Apr 16	May 1	May 15	Oct 10
Rapid CityRapid City, USC00396948	3,379 ft	Apr 20	May 3	May 17	Oct 8
AberdeenAberdeen, USW00014929	1,302 ft	Apr 27	May 9	May 22	Sep 26
BuffaloBuffalo, USW00094037	3,004 ft	Apr 30	May 10	May 23	Oct 1

Crop chart

When to start seeds in South Dakota, spring 2027

Counted back from the median last frost at Rapid City, May 3. Pick another station to redraw the chart for it.

Start indoorsHarden offSet outSow outdoorsMedian last frostLast freeze passed in 9 of 10 years

Every crop, counted from a median last frost of May 3
Crop	Start indoors	Set out	Sow outdoors	Frost class
Tomato	Mar 15 to Mar 29	May 10 to May 17		Tender, very tender
Pepper	Mar 8 to Mar 22	May 17 to May 24		Tender, very tender
Eggplant	Mar 8 to Mar 22	May 17 to May 24		Tender, very tender
Basil	Mar 22 to Apr 5	May 17 to May 24		Tender
Celery	Feb 8 to Feb 22	May 3 to May 10		Tender
Cucumber	Apr 12 to Apr 19	May 10 to May 17	May 3 to May 10	Tender
Summer squash	Apr 19 to Apr 26	May 17 to May 24	May 3 to May 10	Tender
Winter squash	Apr 19 to Apr 26	May 17 to May 24	May 17 to May 24	Tender, very tender
Pumpkin	Apr 19 to Apr 26	May 17 to May 24	May 17 to May 24	Tender, very tender
Melon (cantaloupe)	Apr 19 to Apr 26	May 17 to May 24		Tender, very tender
Watermelon	Apr 12 to Apr 26	May 17 to May 24		Tender, very tender
Onion (from seed)	Jan 25 to Feb 8	Apr 5 to Apr 12		Hardy
Leek	Jan 25 to Feb 8	Apr 5 to Apr 12		Hardy
Parsley	Feb 1 to Feb 8	Apr 12 to Apr 19		Half-hardy
Broccoli	Feb 22 to Mar 8	Apr 5 to Apr 19		Hardy
Brussels sprouts	Feb 22 to Mar 8	Apr 5 to Apr 19		Hardy
Cabbage	Feb 22 to Mar 8	Apr 5 to Apr 12		Hardy
Cauliflower	Mar 8 to Mar 22	Apr 19 to Apr 26		Half-hardy
Kale	Feb 22 to Mar 8	Apr 5 to Apr 12		Hardy
Lettuce	Mar 1 to Mar 8	Apr 5 to Apr 12		Hardy
Swiss chard	Mar 8 to Mar 22	Apr 19 to Apr 26	Apr 5 to Apr 12	Half-hardy
Spinach	Feb 8 to Feb 22	Mar 22 to Apr 12	Apr 5 to Apr 19	Hardy
Peas			Apr 5 to Apr 19	Hardy
Radish			Apr 5 to Apr 19	Hardy
Carrot			Apr 19 to May 3	Half-hardy
Beet			Apr 19 to May 3	Half-hardy
Beans			May 3 to May 10	Tender
Sweet corn			May 3 to May 10	Tender

Six square pots of dark compost seen from above, each holding a single seedling with two narrow seed leaves — Tomato seedlings at the seed leaf stage, one to a pot. The University of Minnesota Extension holds off on fertilizer until a seedling has several sets of true leaves, then feeds at quarter strength once a week. “Tomato Seedlings (49768696597)” by Amanda Slater from Coventry, West Midlands, UK, CC BY-SA 2.0

Extension guide

What SDSU Extension advises

SDSU Extension publishes the planting guide South Dakota gardeners work from, Vegetable Gardening in South Dakota (P-00123).

“Comparing the maps with the table below can help you determine planting dates, as well as the average length of the growing season in your area.”

SDSU Extension, Vegetable Gardening in South Dakota, quoted exactly.

Planting months

SDSU Extension planting months for South Dakota

The extension also publishes planting months by region. Each filled cell is a month the guide gives for planting that crop.

South Dakota (statewide)

Crop	Apr	May	Jun	Jul
tomato		May	Jun
pepper		May	Jun
eggplant		May	Jun
broccoli	Apr	May
cabbage	Apr	May
onion	Apr	May
cucumber		May	Jun
melon		May	Jun
cauliflower	Apr	May	Jun
lettuce	Apr	May
peas	Apr	May
carrot	Apr	May	Jun
beans		May	Jun	Jul
sweet corn		May	Jun	Jul

Planting months from SDSU Extension, Vegetable Gardening in South Dakota, read 2026-09-21. Tomatoes in South Dakota: May and June.

A gardener kneeling beside a raised bed setting a young tomato plant into dark soil, an empty nursery pot beside her — Setting out a tomato in June at a community garden. Tender crops go out after the last frost, and after a week or two of hardening off outdoors. “Volunteer planting heirloom tomato (4704185147)”, Pacific Southwest Region 5, Public domain

Seed starting questions for South Dakota

When should I start seeds indoors in South Dakota?

When is the last frost in South Dakota?

When can I plant tomatoes outside in South Dakota?

What months do I plant vegetables in South Dakota?

What does SDSU Extension say about planting dates in South Dakota?

How many weeks before the last frost do I start peppers and eggplant?

How long do seedlings need to harden off?

Why do seed starting dates differ across South Dakota?

Frost dates from NOAA NCEI U.S. Climate Normals 1991-2020, annual/seasonal, by station (v1.0.1). Planting guidance from SDSU Extension, quoted exactly. Seed starting weeks from UNH Cooperative Extension. Compiled 2026-09-21.

First frost in South DakotaThe other end of the season: when fall frost ends the tender crops.Soil temperatureBeans, corn and squash sown direct wait on warm soil as well as the last frost.South Dakota lawn care calendarSpring seeding, feeding and mowing dates on the same climate.Fall planting calendarGarlic, cool season crops and a second sowing window in the fall.Frost dates by ZIPFirst and last frost odds for any address.