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When to plant watermelons in Okayama: 14 May – 5 September

In Okayama, watermelon: sow for seedlings from 26 March to 8 August; plant into a greenhouse from 23 April to 5 September; plant out into open ground from 14 May to 5 September.

Watermelon in Okayama: soil, season and weather

In Okayama the soil, not frost, sets the date: the last frost is over around 20 March, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 14 May, 55 days later.

Last spring frost20 March
Top 7 cm of soil at 18 °C14 May, 55 days after the last frost
Into an unheated greenhouse23 April – 5 September; April outside: 9 °C at night, 19.1 °C by day; card 18–35 °C
First autumn frost15 December, 215 days after the start
Days in the bed to the first harvest (card)59
First harvest, if planted in this window12 July – 3 November
Days left for picking156
Daylight13:04 on 16 April, 13:56 on 14 May
Watering outdoors when fruiting (card)every 5 days; the driest month, December, has 5 rainy days

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

Watermelon in Okayama: care after planting

Planted on 14 May: in the first weeks water every 5 days.

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

  • 14 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 Okayama during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, August, averages 32.4 °C. Months that stay below 18 °C even by day on average: November (16.7 °C) and December (10.8 °C). Nights average below 18 °C in May and October–December (2.3–14.2 °C).

MonthDay, °CNight, °CRain, mmRainy daysDaylight on the 15th
May23.413.61331013:58
June26.718.32081414:28
July30.523.12301514:16
August32.424.21621313:29
September28.320.81931412:26
October22.414.21151011:21
November16.77.754610:22
December10.82.33759:51

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Okayama, Osaka is 9 days earlier and Hiroshima 12 days later.

CityDistanceDateDifference
Hiroshima138 km26 May – 16 August12 days later
Osaka145 km5 May – 7 September9 days earlier
Kyoto174 km14 May – 28 Augustsame day
Nagoya278 km6 May – 31 August8 days earlier
Kitakyushu292 kmfrom 15 May1 day later
Fukuoka345 km5 May – 11 September9 days earlier

Where to buy watermelon plants and seeds near Okayama

Buy plants ready to set out from 14 May to 5 September (from 23 April to 5 September for an unheated greenhouse); seed for raising your own is sown from 26 March to 8 August. Within 15 km of Okayama OpenStreetMap lists 8 garden centres, 5 farm-supply shops, 3 markets and 19 farm shops (collected 28 October 2026).

Places: © OpenStreetMap contributors, ODbL.

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

When to plant watermelons in Okayama?

In Okayama, watermelon: sow for seedlings from 26 March to 8 August; plant into a greenhouse from 23 April to 5 September; plant out into open ground from 14 May to 5 September.

When to sow watermelons for seedlings in Okayama?

Sow for seedlings from 26 March to 8 August.

When is the last spring frost in Okayama?

Last spring frost around 20 March, first autumn frost around 15 December.

Other crops in Okayama, with their dates