Frost dates and when to plant in South Dakota

United States

In South Dakota the last spring frost comes between 24 April (Sioux Falls) and 7 May (Rapid City) — the median of 2016–2025 in 3 cities. The first autumn frost comes between 12 October (Rapid City) and 24 October (Pierre). The frost-free season lasts 158–181 days. Tomato: plant out into open ground 9 May – 4 July, earliest in Pierre, latest in Pierre.

Frost dates by city in South Dakota

City	Last spring frost	First autumn frost	Frost-free days	Climate zone	Tomato: window
Sioux Falls	24 April	21 October	180	150–209 frost-free days	11 May – 1 July
Pierre	26 April	24 October	181	150–209 frost-free days	9 May – 4 July
Rapid City	7 May	12 October	158	150–209 frost-free days	20 May – 22 June

Median of 2016–2025 for the 25 km grid cell of the city: the last day at or below 0 °C in spring and the first in autumn (ERA5 reanalysis via Open-Meteo). In a cold year a frost can come a week or two later — Greenly warns 48 hours ahead.

When to plant in South Dakota: windows by crop

The earliest start and the latest end among the cities here, each with its city; every city’s own window is on its page. Each window starts on the Greenly calendar date and ends on the last day that still leaves the crop’s days to harvest (from its card) before the average first autumn frost, plus six weeks of picking for crops harvested over weeks (tomatoes, peppers, aubergines, cucumbers, courgettes, pumpkins, watermelons, beans) — our rule; earlier in the window is safer.

Crop	Planting out or sowing
Tomato	9 May (Pierre) – 4 July (Pierre)
Cucumber	24 May (Sioux Falls) – 9 August (Pierre)
Bell Pepper, Eggplant	24 May (Sioux Falls) – 4 July (Pierre)
Zucchini	24 May (Sioux Falls) – 7 August (Pierre)
Pumpkin	24 May (Sioux Falls) – 29 June (Pierre)
Watermelon	24 May (Sioux Falls) – 15 July (Pierre)
Peas	3 April (Sioux Falls) – 11 August (Pierre)
Garlic, Tulip, Daffodil, Crocus, Hyacinth	Autumn planting: 12 September (Rapid City) – 28 November (Rapid City)

Weather by month in South Dakota

Across the 3 cities the warmest month is July (average days 29.2 … 31.7 °C) and the coldest January (average nights -11 … -7 °C). Every city averages below 0 °C at night in November–March.

Month	Day, °C	Night, °C	Rain, mm
January	-2.3 … 3.3 °C	-11 … -7 °C	13
February	0.2 … 2.7 °C	-10.2 … -8.7 °C	21
March	8.3 … 9.2 °C	-3 … -2.8 °C	34
April	13.5 … 14.4 °C	0.7 … 2.5 °C	67
May	19 … 21.8 °C	7.3 … 10 °C	86
June	26.5 … 29.3 °C	13.8 … 17 °C	69
July	29.2 … 31.7 °C	16.8 … 19.7 °C	68
August	27.5 … 30.2 °C	15.9 … 18.4 °C	59
September	24.9 … 26.3 °C	12.3 … 14.5 °C	50
October	15.9 … 16.5 °C	4.5 … 6 °C	41
November	7.8 … 9.6 °C	-1.4 … -0.9 °C	19
December	0.9 … 4.4 °C	-7.7 … -5.7 °C	29

Day and night: the lowest … highest monthly average among the cities; rain: the middle city (ERA5 via Open-Meteo).

Frost dates and when to plant in South Dakota

Frost dates by city in South Dakota

When to plant in South Dakota: windows by crop

Weather by month in South Dakota

What to plant month by month: the Northeast and Midwest

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