When to plant watermelons in Nagoya: 6 May – 31 August

In Nagoya, watermelon: sow for seedlings from 18 March to 3 August; plant into a greenhouse from 15 April to 31 August; plant out into open ground from 6 May to 31 August.

Watermelon in Nagoya: soil, season and weather

In Nagoya the soil, not frost, sets the date: the last frost is over around 22 March, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 6 May, 45 days later.

Last spring frost	22 March
Top 7 cm of soil at 18 °C	6 May, 45 days after the last frost
Into an unheated greenhouse	15 April – 31 August; April outside: 9.1 °C at night, 19 °C by day; card 18–35 °C
First autumn frost	10 December, 218 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	4 July – 29 October
Days left for picking	159
Daylight	12:49 on 8 April, 13:45 on 6 May
Watering outdoors when fruiting (card)	every 5 days; the driest month, December, has 8 rainy days

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

Watermelon in Nagoya: care after planting

Planted on 6 May: in the first weeks water every 5 days.

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

6 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 Nagoya during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, August, averages 32.2 °C. Months that stay below 18 °C even by day on average: November (16.6 °C) and December (10.7 °C). Nights average below 18 °C in May and October–December (1.9–13.9 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	23.2	13.6	189	11	14:00
June	26.5	18.3	250	15	14:31
July	30.2	22.8	301	17	14:19
August	32.2	24	211	17	13:30
September	28.2	20.8	214	16	12:26
October	22.1	13.9	190	11	11:20
November	16.6	7.5	88	8	10:20
December	10.7	1.9	57	8	9:48

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Nagoya, Tokyo is 8 days earlier and Niigata 14 days later.

City	Distance	Date	Difference
Hamamatsu	92 km	2 May – 8 September	4 days earlier
Kyoto	105 km	14 May – 28 August	8 days later
Osaka	139 km	5 May – 7 September	1 day earlier
Tokyo	259 km	28 April – 4 September	8 days earlier
Okayama	278 km	14 May – 5 September	8 days later
Niigata	360 km	20 May – 10 September	14 days later

Where to buy watermelon plants and seeds near Nagoya

Buy plants ready to set out from 6 May to 31 August (from 15 April to 31 August for an unheated greenhouse); seed for raising your own is sown from 18 March to 3 August. Within 15 km of Nagoya OpenStreetMap lists 7 garden centres, 8 markets and 1 farm shop (collected 28 October 2026).

名古屋市中央卸売市場南部市場 — market
12 km · city.nagoya.jp
Central wholesale market of the city of Nagoya — market
5 km
名古屋古書会館 — market
3 km
金城市場 — market
2 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