When to plant watermelons in Madison: 28 May – 18 July

In Madison, watermelon: sow for seedlings from 9 April to 20 June; plant into a greenhouse from 7 May to 18 July; plant out into open ground from 28 May to 18 July.

Watermelon in Madison: soil, season and weather

In Madison the soil, not frost, sets the date: the last frost is over around 27 April, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 28 May, 31 days later.

Last spring frost	27 April
Top 7 cm of soil at 18 °C	28 May, 31 days after the last frost
Into an unheated greenhouse	7 May – 18 July; May outside: 9.9 °C at night, 20.6 °C by day; card 18–35 °C
First autumn frost	27 October, 152 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	26 July – 15 September
Days left for picking	93
Daylight	14:03 on 30 April, 15:03 on 28 May
Watering outdoors when fruiting (card)	every 5 days; the driest month, August, has 10 rainy days

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

Watermelon in Madison: care after planting

Planted on 28 May: in the first weeks water every 5 days.

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

28 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 Madison during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, July, averages 27.9 °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 (7.4–17.3 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	20.6	9.9	105	12	14:39
June	26.5	16.2	107	12	15:21
July	27.9	18.4	99	11	15:04
August	26.7	17.3	79	10	13:59
September	23.6	14.3	90	8	12:33
October	16	7.4	85	10	11:06

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

3 of the nearest cities share Madison's date.

City	Distance	Date	Difference
Rockford	94 km	28 May – 19 July	same day
Milwaukee	121 km	28 May – 23 July	same day
Davenport	195 km	17 May – 21 July	11 days earlier
Green Bay	196 km	27 May – 21 July	1 day earlier
Chicago	196 km	28 May – 28 July	same day
Cedar Rapids	224 km	20 May – 16 July	8 days earlier

Where to buy watermelon plants and seeds near Madison

Buy plants ready to set out from 28 May to 18 July (from 7 May to 18 July for an unheated greenhouse); seed for raising your own is sown from 9 April to 20 June. Within 15 km of Madison OpenStreetMap lists 8 garden centres, 1 farm-supply shop, 3 plant nurseries, 19 markets and 1 farm shop (collected 20 October 2026).

Nursery — plant nursery
4 km
Research — plant nursery
4 km
Urban Gardens and Greenhouse — plant nursery
8 km
Metrogro — farm supply
6 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