When to plant watermelons in Jefferson City: 11 May – 26 July

In Jefferson City, watermelon: sow for seedlings from 23 March to 28 June; plant into a greenhouse from 20 April to 26 July; plant out into open ground from 11 May to 26 July.

Watermelon in Jefferson City: soil, season and weather

In Jefferson City the soil, not frost, sets the date: the last frost is over around 5 April, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 11 May, 36 days later.

Last spring frost	5 April
Top 7 cm of soil at 18 °C	11 May, 36 days after the last frost
Into an unheated greenhouse	20 April – 26 July; April outside: 8 °C at night, 19.9 °C by day; card 18–35 °C
First autumn frost	4 November, 177 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	9 July – 23 September
Days left for picking	118
Daylight	13:06 on 13 April, 14:08 on 11 May
Watering outdoors when fruiting (card)	every 5 days; the driest month, November, has 7 rainy days

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

Watermelon in Jefferson City: care after planting

Planted on 11 May: in the first weeks water every 5 days.

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

11 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 Jefferson City during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, July, averages 31.9 °C. Months that stay below 18 °C even by day on average: November (14 °C). Nights average below 18 °C in May and September–November (4.1–17.4 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	24.5	14	124	14	14:15
June	30.6	19.4	122	11	14:51
July	31.9	21.5	111	11	14:37
August	30.6	20.3	100	10	13:42
September	28.4	17.4	66	7	12:29
October	21.4	10.9	95	9	11:15
November	14	4.1	64	7	10:06

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Jefferson City, Joplin is 6 days earlier and Peoria 7 days later.

City	Distance	Date	Difference
St. Louis	172 km	8 May – 26 July	3 days earlier
Kansas City	216 km	7 May – 23 July	4 days earlier
Springfield	258 km	15 May – 23 July	4 days later
Joplin	263 km	5 May – 23 July	6 days earlier
Topeka	309 km	6 May – 20 July	5 days earlier
Peoria	324 km	18 May – 22 July	7 days later

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.

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