When to plant watermelons in Allentown: 23 May – 25 July

In Allentown, watermelon: sow for seedlings from 4 April to 27 June; plant into a greenhouse from 2 May to 25 July; plant out into open ground from 23 May to 25 July.

Watermelon in Allentown: soil, season and weather

In Allentown the soil, not frost, sets the date: the last frost is over around 15 April, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 23 May, 38 days later.

Last spring frost	15 April
Top 7 cm of soil at 18 °C	23 May, 38 days after the last frost
Into an unheated greenhouse	2 May – 25 July; May outside: 10.8 °C at night, 21.6 °C by day; card 18–35 °C
First autumn frost	3 November, 164 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	21 July – 22 September
Days left for picking	105
Daylight	13:41 on 25 April, 14:40 on 23 May
Watering outdoors when fruiting (card)	every 5 days; the driest month, November, has 9 rainy days

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

Watermelon in Allentown: care after planting

Planted on 23 May: in the first weeks water every 5 days.

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

23 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 Allentown during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, July, averages 30.2 °C. Months that stay below 18 °C even by day on average: November (11.3 °C). Nights average below 18 °C in May, June and September–November (2.4–15.9 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	21.6	10.8	120	13	14:25
June	26.9	15.9	101	12	15:04
July	30.2	19.6	125	14	14:49
August	28.2	18.3	127	13	13:49
September	24.9	14.9	106	10	12:30
October	18.7	9.2	93	9	11:11
November	11.3	2.4	80	9	9:57

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Allentown, Atlantic City is 18 days earlier and Harrisburg 2 days later.

City	Distance	Date	Difference
Trenton	73 km	21 May – 3 August	2 days earlier
Philadelphia	77 km	14 May – 2 August	9 days earlier
Harrisburg	124 km	25 May – 2 August	2 days later
New York	125 km	21 May – 11 August	2 days earlier
Dover	160 km	11 May – 17 August	12 days earlier
Atlantic City	165 km	5 May – 13 August	18 days earlier

Where to buy watermelon plants and seeds near Allentown

Buy plants ready to set out from 23 May to 25 July (from 2 May to 25 July for an unheated greenhouse); seed for raising your own is sown from 4 April to 27 June. Within 15 km of Allentown OpenStreetMap lists 14 garden centres, 1 plant nursery, 6 markets and 7 farm shops (collected 29 October 2026).

Saucon Valley Farmer's Market — market
12 km
Trexlertown Farmer's Market — market
13 km
Strawberry Acres — farm shop
13 km
Bechdolt's Orchards — farm shop
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.

Questions