When to plant watermelons in Southampton: 17 June – 14 August

In Southampton, watermelon: sow for seedlings from 29 April to 17 July; plant into a greenhouse from 27 May to 14 August; plant out into open ground from 17 June to 14 August.

Watermelon in Southampton: soil, season and weather

In Southampton the soil, not frost, sets the date: the last frost is over around 4 April, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 17 June, 74 days later.

Last spring frost	4 April
Top 7 cm of soil at 18 °C	17 June, 74 days after the last frost
Into an unheated greenhouse	27 May – 14 August; May outside: 8.2 °C at night, 17.4 °C by day; card 18–35 °C
First autumn frost	23 November, 159 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	15 August – 12 October
Days left for picking	100
Daylight	15:44 on 20 May, 16:31 on 17 June
Watering outdoors when fruiting (card)	every 5 days; the driest month, July, has 10 rainy days

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

Watermelon in Southampton: care after planting

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

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

17 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 Southampton 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 (15.4 °C) and November (11.1 °C). Nights average below 18 °C in every month of the season, from 5.2 °C to 13.5 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
June	20.5	11.5	59	11	16:30
July	22.3	13.5	54	10	16:06
August	21.8	13.3	60	10	14:36
September	19.2	11.2	73	11	12:42
October	15.4	8.8	100	13	10:47
November	11.1	5.2	86	13	8:58

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Southampton, London is 5 days earlier and Brighton 33 days later.

City	Distance	Date	Difference
Portsmouth	24 km	16 June – 22 August	1 day earlier
Brighton	89 km	20 July – 22 August	33 days later
Oxford	95 km	23 June – 14 August	6 days later
Bristol	103 km	19 June – 13 August	2 days later
London	111 km	12 June – 14 August	5 days earlier
Cardiff	140 km	24 June – 13 August	7 days later

Where to buy watermelon plants and seeds near Southampton

Buy plants ready to set out from 17 June to 14 August (from 27 May to 14 August for an unheated greenhouse); seed for raising your own is sown from 29 April to 17 July. Within 15 km of Southampton OpenStreetMap lists 28 garden centres, 15 plant nurseries, 1 market and 10 farm shops (collected 20 October 2026).

Chichester Trees & Shrubs — plant nursery
8 km
Fairweather's Nursery — plant nursery
8 km
New Forest Plants — plant nursery
9 km
Shelley Nursery — plant nursery
12 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