When to plant watermelons in San Sebastián: 8 June – 24 August

In San Sebastián, watermelon: sow for seedlings from 20 April to 27 July; plant into a greenhouse from 18 May to 24 August; plant out into open ground from 8 June to 24 August. For plants and seeds, the places nearby include Olasagasti (farm shop, 6 km); addresses and opening hours are below.

Watermelon in San Sebastián: soil, season and weather

In San Sebastián the soil, not frost, sets the date: the last frost is over around 22 January, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 8 June, 137 days later.

Last spring frost	22 January
Top 7 cm of soil at 18 °C	8 June, 137 days after the last frost
Into an unheated greenhouse	18 May – 24 August; May outside: 10.7 °C at night, 18.2 °C by day; card 18–35 °C
First autumn frost	3 December, 178 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	6 August – 22 October
Days left for picking	119
Daylight	14:31 on 11 May, 15:18 on 8 June
Watering outdoors when fruiting (card)	every 5 days; the driest month, July, has 13 rainy days

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

Watermelon in San Sebastián: care after planting

Planted on 8 June: in the first weeks water every 5 days.

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

8 June — 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 San Sebastián during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, August, averages 23.6 °C. Months that stay below 18 °C even by day on average: November (14.7 °C) and December (12.8 °C). Nights average below 18 °C in every month of the season, from 6.9 °C to 16.3 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
June	21.3	14.2	109	14	15:23
July	22.7	16	73	13	15:06
August	23.6	16.3	99	12	14:00
September	22.1	14.3	127	13	12:33
October	19.7	12.4	139	13	11:05
November	14.7	8.6	230	18	9:44
December	12.8	6.9	189	15	9:00

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

All the nearest cities on our list plant watermelon earlier than San Sebastián; the closest date is in Vitoria-Gasteiz, 4 days earlier.

City	Distance	Date	Difference
Bayonne	45 km	28 May – 7 September	11 days earlier
Pamplona	63 km	1 June – 21 August	7 days earlier
Vitoria-Gasteiz	77 km	4 June – 15 August	4 days earlier
Bilbao	77 km	2 June – 16 September	6 days earlier
Logroño	102 km	28 May – 25 August	11 days earlier
Pau	131 km	2 June – 25 August	6 days earlier

Where to buy watermelon plants and seeds near San Sebastián

Buy plants ready to set out from 8 June to 24 August (from 18 May to 24 August for an unheated greenhouse); seed for raising your own is sown from 20 April to 27 July. Within 15 km of San Sebastián OpenStreetMap lists 4 garden centres, 3 farm-supply shops, 6 markets and 4 farm shops (collected 27 October 2026).

Olasagasti — farm shop
Akarregi 12, 20120 Hernani · 6 km
Alkubi Garden — garden centre
3 km · alkubigarden.com
Aduna Garden — garden centre
14 km · endanea.com
Agrícola Txema — farm supply
9 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