When to plant watermelons in Sioux Falls: 24 May – 12 July

In Sioux Falls, watermelon: sow for seedlings from 5 April to 14 June; plant into a greenhouse from 3 May to 12 July; plant out into open ground from 24 May to 12 July.

Watermelon in Sioux Falls: soil, season and weather

In Sioux Falls the soil, not frost, sets the date: the last frost is over around 24 April, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 24 May, 30 days later.

Last spring frost	24 April
Top 7 cm of soil at 18 °C	24 May, 30 days after the last frost
Into an unheated greenhouse	3 May – 12 July; May outside: 10 °C at night, 21.5 °C by day; card 18–35 °C
First autumn frost	21 October, 150 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	22 July – 9 September
Days left for picking	91
Daylight	13:55 on 26 April, 14:59 on 24 May
Watering outdoors when fruiting (card)	every 5 days; the driest month, September, has 8 rainy days

The same dates in Sioux Falls hold for Cucumber, Bell Pepper, Eggplant, Zucchini and Pumpkin.

Watermelon in Sioux Falls: care after planting

Planted on 24 May: in the first weeks water every 5 days.

Feeding, by the card’s schedule from that day:

24 May — feed: balanced (NPK)

Pests and diseases of watermelon to watch for:

Dates count from the first planting day of the window above; a later planting moves them by as many days.

Weather in Sioux Falls during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, July, averages 29.2 °C. Months that stay below 18 °C even by day on average: October (16 °C). Nights average below 18 °C in May, June and August–October (6–17.5 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	21.5	10	108	11	14:41
June	28.2	16.9	110	11	15:24
July	29.2	18.6	71	8	15:07
August	27.5	17.5	90	10	14:01
September	25.1	14.5	64	8	12:33
October	16	6	67	8	11:05

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Sioux Falls, Lincoln is 13 days earlier and Minneapolis 4 days later.

City	Distance	Date	Difference
Omaha	262 km	17 May – 17 July	7 days earlier
Pierre	302 km	25 May – 15 July	1 day later
Lincoln	304 km	11 May – 19 July	13 days earlier
Minneapolis	319 km	28 May – 15 July	4 days later
Grand Island	321 km	18 May – 18 July	6 days earlier
Des Moines	334 km	17 May – 18 July	7 days earlier

Where to buy watermelon plants and seeds near Sioux Falls

Buy plants ready to set out from 24 May to 12 July (from 3 May to 12 July for an unheated greenhouse); seed for raising your own is sown from 5 April to 14 June. Within 15 km of Sioux Falls OpenStreetMap lists 1 garden centre, 5 farm-supply shops, 2 markets and 1 farm shop (collected 20 October 2026).

AgReliant Genetics — farm supply
13 km
Riekes Equipment — farm supply
13 km
New Direction Equipment — farm supply
13 km
The Prairie Farmers' Market — market
North Cherapa Place 300, 57104 Sioux Falls · 1 km · theprairiefarmersmarket.com

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.

Questions