When to plant watermelons in Viana do Castelo: 30 May – 2 September

In Viana do Castelo, watermelon: sow for seedlings from 11 April to 5 August; plant into a greenhouse from 9 May to 2 September; plant out into open ground from 30 May to 2 September.

Watermelon in Viana do Castelo: soil, season and weather

In Viana do Castelo the soil, not frost, sets the date: the last frost is over around 3 February, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 30 May, 116 days later.

Last spring frost	3 February
Top 7 cm of soil at 18 °C	30 May, 116 days after the last frost
Into an unheated greenhouse	9 May – 2 September; May outside: 10 °C at night, 19.1 °C by day; card 18–35 °C
First autumn frost	12 December, 196 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	28 July – 31 October
Days left for picking	137
Daylight	14:02 on 2 May, 14:57 on 30 May
Watering outdoors when fruiting (card)	every 5 days; the driest month, July, has 4 rainy days

The same dates in Viana do Castelo hold for Cucumber, Bell Pepper, Eggplant, Zucchini and Pumpkin.

Watermelon in Viana do Castelo: care after planting

Planted on 30 May: in the first weeks water every 5 days.

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

30 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 Viana do Castelo during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, August, averages 24.8 °C. Months that stay below 18 °C even by day on average: November (14.5 °C) and December (12.7 °C). Nights average below 18 °C in every month of the season, from 5.7 °C to 14.8 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	19.1	10	128	11	14:31
June	21.1	12.6	77	10	15:11
July	24.4	14.8	22	4	14:55
August	24.8	14.8	33	4	13:53
September	22.4	13.1	95	9	12:31
October	19.2	11.2	268	13	11:09
November	14.5	7.7	265	16	9:52
December	12.7	5.7	272	16	9:11

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Viana do Castelo, Vigo is 21 days earlier and Ourense 2 days later.

City	Distance	Date	Difference
Braga	37 km	24 May – 13 September	6 days earlier
Vigo	61 km	from 9 May	21 days earlier
Porto	63 km	22 May – 9 September	8 days earlier
Pontevedra	84 km	from 26 May	4 days earlier
Vila Real	101 km	18 May – 12 September	12 days earlier
Ourense	108 km	1 June – 24 August	2 days later

Where to buy watermelon plants and seeds near Viana do Castelo

Buy plants ready to set out from 30 May to 2 September (from 9 May to 2 September for an unheated greenhouse); seed for raising your own is sown from 11 April to 5 August. Within 15 km of Viana do Castelo OpenStreetMap lists 1 farm-supply shop, 1 plant nursery and 3 markets (collected 27 October 2026).

Zona de Atividades Económicas de Darque — market
2 km
Mercado Municipal de Vila Praia de Âncora — market
Mon, Tue, Wed, Fri, Sat 08:00–18:00; Thu 07:00–18:00 · 14 km
Viveiro — plant nursery
5 km
Casa do Lavrador — farm supply
14 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