When to plant watermelons in Gangneung: 17 May – 12 August

In Gangneung, watermelon: sow for seedlings from 29 March to 15 July; plant into a greenhouse from 26 April to 12 August; plant out into open ground from 17 May to 12 August.

Watermelon in Gangneung: soil, season and weather

In Gangneung the soil, not frost, sets the date: the last frost is over around 19 March, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 17 May, 59 days later.

Last spring frost	19 March
Top 7 cm of soil at 18 °C	17 May, 59 days after the last frost
Into an unheated greenhouse	26 April – 12 August; April outside: 8.2 °C at night, 16.9 °C by day; card 18–35 °C
First autumn frost	21 November, 188 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	15 July – 10 October
Days left for picking	129
Daylight	13:18 on 19 April, 14:15 on 17 May
Watering outdoors when fruiting (card)	every 5 days; the driest month, November, has 6 rainy days

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

Watermelon in Gangneung: care after planting

Planted on 17 May: in the first weeks water every 5 days.

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

17 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 Gangneung during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, August, averages 28.4 °C. Months that stay below 18 °C even by day on average: November (13.1 °C). Nights average below 18 °C in May (13.3 °C), October (11.6 °C) and November (5.1 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	21.6	13.3	75	9	14:11
June	25	18.1	100	10	14:46
July	27.9	22.4	229	15	14:32
August	28.4	22.8	307	17	13:39
September	23.9	18	226	15	12:28
October	18.4	11.6	172	12	11:16
November	13.1	5.1	48	6	10:10

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Gangneung, Seoul is 2 days earlier and Chuncheon 7 days later.

City	Distance	Date	Difference
Chuncheon	103 km	24 May – 22 July	7 days later
Seoul	169 km	15 May – 28 July	2 days earlier
Daejeon	205 km	17 May – 3 August	same day
Daegu	211 km	16 May – 12 August	1 day earlier
Ulsan	248 km	18 May – 7 August	1 day later
Jeonju	265 km	19 May – 8 August	2 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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