When to plant watermelons in Sapporo: 17 July – 19 August

In Sapporo, watermelon: sow for seedlings from 29 May to 22 July; plant into a greenhouse from 26 June to 19 August; plant out into open ground from 17 July to 19 August. For plants and seeds, the places nearby include 萩野農園野菜直売所果菜園 (farm shop, 13 km); addresses and opening hours are below.

Watermelon in Sapporo: soil, season and weather

In Sapporo the soil, not frost, sets the date: the last frost is over around 9 May, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 17 July, 69 days later. 92 days separate planting out (17 July) from the first autumn frost (17 October); the card's 59 days to the first harvest leave 33 for picking, so a start 4 weeks late would still fit.

Last spring frost	9 May
Top 7 cm of soil at 18 °C	17 July, 69 days after the last frost
Into an unheated greenhouse	26 June – 19 August; June outside: 9.6 °C at night, 17.8 °C by day; card 18–35 °C
First autumn frost	17 October, 92 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	14 September – 17 October
Days left for picking	33
Daylight	15:22 on 19 June, 15:01 on 17 July
Watering outdoors when fruiting (card)	every 5 days; the driest month, October, has 14 rainy days

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

Watermelon in Sapporo: care after planting

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

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

17 July — 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 Sapporo during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, July, averages 22.3 °C. Months that stay below 18 °C even by day on average: October (10.9 °C). Nights average below 18 °C in every month of the season, from 3.3 °C to 15.2 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
July	22.3	14.8	151	16	15:04
August	22.1	15.2	200	17	13:59
September	18.1	10.6	139	13	12:33
October	10.9	3.3	120	14	11:06

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

All the nearest cities on our list plant watermelon earlier than Sapporo; the closest date is in Vladivostok, 11 days earlier.

City	Distance	Date	Difference
Sendai	534 km	7 June – 14 August	40 days earlier
Niigata	604 km	20 May – 10 September	58 days earlier
Vladivostok	768 km	6 July – 27 July	11 days earlier
Khabarovsk	774 km	15 June – 7 July	32 days earlier
Tokyo	832 km	28 April – 4 September	80 days earlier
Nagoya	956 km	6 May – 31 August	72 days earlier

Where to buy watermelon plants and seeds near Sapporo

Buy plants ready to set out from 17 July to 19 August (from 26 June to 19 August for an unheated greenhouse); seed for raising your own is sown from 29 May to 22 July. Within 15 km of Sapporo OpenStreetMap lists 2 garden centres, 1 farm-supply shop, 2 markets and 3 farm shops (collected 28 October 2026).

Nijo Market — market
Mon–Sun 07:00–18:00 · 1 km · nijomarket.com
萩野農園野菜直売所果菜園 — farm shop
09:00–19:00 · 13 km
Joyful AK — garden centre
9 km
ヤマグチガーデン — garden centre
4 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.

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