When to plant watermelons in Viseu: 27 May – 31 August

In Viseu, watermelon: sow for seedlings from 8 April to 3 August; plant into a greenhouse from 6 May to 31 August; plant out into open ground from 27 May to 31 August.

Watermelon in Viseu: soil, season and weather

In Viseu the soil, not frost, sets the date: the last frost is over around 7 February, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 27 May, 109 days later.

Last spring frost	7 February
Top 7 cm of soil at 18 °C	27 May, 109 days after the last frost
Into an unheated greenhouse	6 May – 31 August; May outside: 10.2 °C at night, 21.3 °C by day; card 18–35 °C
First autumn frost	10 December, 197 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	25 July – 29 October
Days left for picking	138
Daylight	13:51 on 29 April, 14:46 on 27 May
Watering outdoors when fruiting (card)	every 5 days; the driest month, July, has 2 rainy days

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

Watermelon in Viseu: care after planting

Planted on 27 May: in the first weeks water every 5 days.

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

27 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 Viseu during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, August, averages 30 °C. Months that stay below 18 °C even by day on average: November (15 °C) and December (12.8 °C). Nights average below 18 °C in every month of the season, from 5.1 °C to 15.9 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	21.3	10.2	73	11	14:26
June	24.6	13.1	49	8	15:04
July	29.1	15.6	9	2	14:49
August	30	15.9	9	2	13:49
September	25.4	13.6	57	6	12:30
October	21.2	11.6	152	12	11:11
November	15	7.2	156	14	9:57
December	12.8	5.1	153	13	9:17

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Viseu, Castelo Branco is 27 days earlier and Guarda 1 day later.

City	Distance	Date	Difference
Guarda	56 km	28 May – 16 August	1 day later
Coimbra	67 km	from 12 May	15 days earlier
Vila Real	73 km	18 May – 12 September	9 days earlier
Porto	80 km	22 May – 9 September	5 days earlier
Castelo Branco	100 km	30 April – 16 September	27 days earlier
Braga	108 km	24 May – 13 September	3 days earlier

Where to buy watermelon plants and seeds near Viseu

Buy plants ready to set out from 27 May to 31 August (from 6 May to 31 August for an unheated greenhouse); seed for raising your own is sown from 8 April to 3 August. Within 15 km of Viseu OpenStreetMap lists 1 garden centre, 6 farm-supply shops and 4 markets (collected 27 October 2026).

Viseu Garden Centre — garden centre
2 km
Loja do Lavrador — farm supply
1 km
Casgril — farm supply
1 km
Carbovete - Técnica Agro-Pecuária — farm supply
1 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