When to plant watermelons in Grand Island: 18 May – 18 July

In Grand Island, watermelon: sow for seedlings from 30 March to 20 June; plant into a greenhouse from 27 April to 18 July; plant out into open ground from 18 May to 18 July.

Watermelon in Grand Island: soil, season and weather

In Grand Island the soil, not frost, sets the date: the last frost is over around 19 April, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 18 May, 29 days later.

Last spring frost	19 April
Top 7 cm of soil at 18 °C	18 May, 29 days after the last frost
Into an unheated greenhouse	27 April – 18 July; April outside: 4.8 °C at night, 17.7 °C by day; card 18–35 °C
First autumn frost	27 October, 162 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	16 July – 15 September
Days left for picking	103
Daylight	13:30 on 20 April, 14:33 on 18 May
Watering outdoors when fruiting (card)	every 5 days; the driest month, September, has 6 rainy days

The same dates in Grand Island hold for Cucumber, Bell Pepper, Eggplant, Zucchini and Pumpkin.

Watermelon in Grand Island: care after planting

Planted on 18 May: in the first weeks water every 5 days.

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

18 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 Grand Island during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, July, averages 30.5 °C. Nights average below 18 °C in May (11.3 °C), September (15.8 °C) and October (7.4 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	22.7	11.3	127	13	14:27
June	29.8	18.3	86	8	15:06
July	30.5	20	72	8	14:51
August	29.5	18.9	59	8	13:50
September	26.9	15.8	57	6	12:31
October	18.6	7.4	61	6	11:10

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Grand Island, Wichita is 16 days earlier and Sioux Falls 6 days later.

City	Distance	Date	Difference
Lincoln	143 km	11 May – 19 July	7 days earlier
Omaha	206 km	17 May – 17 July	1 day earlier
Topeka	309 km	6 May – 20 July	12 days earlier
Sioux Falls	321 km	24 May – 12 July	6 days later
Wichita	370 km	2 May – 21 July	16 days earlier
Dodge City	379 km	4 May – 20 July	14 days earlier

Where to buy watermelon plants and seeds near Grand Island

Buy plants ready to set out from 18 May to 18 July (from 27 April to 18 July for an unheated greenhouse); seed for raising your own is sown from 30 March to 20 June. Within 15 km of Grand Island OpenStreetMap lists 2 garden centres (collected 28 October 2026).

Ace Hardware & Garden Center — garden centre
0 km
Walmart Garden Center — garden centre
4 km

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