When to plant watermelons in Castelo Branco: 30 April – 16 September

In Castelo Branco, watermelon: sow for seedlings from 12 March to 19 August; plant into a greenhouse from 9 April to 16 September; plant out into open ground from 30 April to 16 September. For plants and seeds, the places nearby include Agriloja (farm supply, 4 km); addresses and opening hours are below.

Watermelon in Castelo Branco: soil, season and weather

In Castelo Branco the soil, not frost, sets the date: the last frost is over around 17 January, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 30 April, 103 days later.

Last spring frost	17 January
Top 7 cm of soil at 18 °C	30 April, 103 days after the last frost
Into an unheated greenhouse	9 April – 16 September; April outside: 9.6 °C at night, 21 °C by day; card 18–35 °C
First autumn frost	26 December, 240 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	28 June – 14 November
Days left for picking	181
Daylight	12:41 on 2 April, 13:50 on 30 April
Watering outdoors when fruiting (card)	every 5 days; the driest month, August, has 1 rainy day

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

Watermelon in Castelo Branco: care after planting

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

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

30 April — 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 Castelo Branco during the watermelon season

Days average above the watermelon card's 18–35 °C in August (35.1 °C). Months that stay below 18 °C even by day on average: November (17.4 °C) and December (14.7 °C). Nights average below 18 °C in April–June and September–December (6.5–16.4 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
April	21	9.6	77	11	13:14
May	25.5	12.8	46	6	14:21
June	29.8	16.1	32	5	14:59
July	34.6	18.9	3	1	14:44
August	35.1	19.2	2	1	13:46
September	29.5	16.4	36	5	12:30
October	24.7	13.7	84	9	11:12
November	17.4	8.9	103	11	10:00
December	14.7	6.5	93	9	9:22

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

All the nearest cities on our list plant watermelon later than Castelo Branco; the closest date is in Badajoz, 3 days later.

City	Distance	Date	Difference
Guarda	82 km	28 May – 16 August	28 days later
Coimbra	91 km	from 12 May	12 days later
Viseu	100 km	27 May – 31 August	27 days later
Cáceres	103 km	8 May – 14 September	8 days later
Leiria	113 km	from 12 May	12 days later
Badajoz	114 km	3 May – 6 September	3 days later

Where to buy watermelon plants and seeds near Castelo Branco

Buy plants ready to set out from 30 April to 16 September (from 9 April to 16 September for an unheated greenhouse); seed for raising your own is sown from 12 March to 19 August. Within 15 km of Castelo Branco OpenStreetMap lists 1 garden centre, 2 farm-supply shops and 2 markets (collected 27 October 2026).

Mercado Municipal — market
0 km
Agriloja — farm supply
Rua R LT 32, 6000-790 Castelo Branco · Mon–Sat 08:30–20:00; Sun 09:00–13:00 · 4 km · agriloja.pt
A Minha Planta — garden centre
3 km
Quinta do Claude Chão da Raia — farm supply
15 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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