When to plant watermelons in London (Canada): 29 May – 29 July

In London (Canada), watermelon: sow for seedlings from 10 April to 1 July; plant into a greenhouse from 8 May to 29 July; plant out into open ground from 29 May to 29 July.

Watermelon in London (Canada): soil, season and weather

In London (Canada) the soil, not frost, sets the date: the last frost is over around 28 April, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 29 May, 31 days later.

Last spring frost	28 April
Top 7 cm of soil at 18 °C	29 May, 31 days after the last frost
Into an unheated greenhouse	8 May – 29 July; May outside: 9 °C at night, 19.7 °C by day; card 18–35 °C
First autumn frost	7 November, 162 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	27 July – 26 September
Days left for picking	103
Daylight	14:05 on 1 May, 15:04 on 29 May
Watering outdoors when fruiting (card)	every 5 days; the driest month, September, has 9 rainy days

The same dates in London (Canada) hold for Cucumber, Bell Pepper, Eggplant, Zucchini and Pumpkin.

Watermelon in London (Canada): care after planting

Planted on 29 May: in the first weeks water every 5 days.

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

29 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 London (Canada) during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, July, averages 27 °C. Months that stay below 18 °C even by day on average: October (15.9 °C) and November (7.9 °C). Nights average below 18 °C in every month of the season, from 1.1 °C to 17.4 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	19.7	9	82	12	14:38
June	25	14.6	90	11	15:20
July	27	17.4	103	12	15:04
August	25.7	16.8	98	13	13:58
September	22.8	13.8	62	9	12:33
October	15.9	7.9	97	13	11:06
November	7.9	1.1	73	13	9:45

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around London (Canada), Windsor is 2 days earlier and Hamilton 3 days later.

City	Distance	Date	Difference
Kitchener	77 km	31 May – 17 July	2 days later
Hamilton	116 km	1 June – 29 July	3 days later
Erie	133 km	30 May – 10 August	1 day later
Windsor	165 km	27 May – 29 July	2 days earlier
Detroit	165 km	27 May – 29 July	2 days earlier
Toronto	167 km	29 May – 21 July	same day

Where to buy watermelon plants and seeds near London (Canada)

Buy plants ready to set out from 29 May to 29 July (from 8 May to 29 July for an unheated greenhouse); seed for raising your own is sown from 10 April to 1 July. Within 15 km of London (Canada) OpenStreetMap lists 5 garden centres, 3 markets and 2 farm shops (collected 20 October 2026).

Heeman's — garden centre
11 km · heeman.ca
Home Depot Garden Center — garden centre
7 km
Springbank Garden Centre — garden centre
5 km
Canadian Tire Garden Center — garden centre
6 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