When to plant watermelons in Río Cuarto: 29 September – 4 March

In Río Cuarto, watermelon: sow for seedlings from 11 August to 5 February; plant into a greenhouse from 8 September to 4 March; plant out into open ground from 29 September to 4 March.

Watermelon in Río Cuarto: soil, season and weather

In Río Cuarto the soil, not frost, sets the date: the last frost is over around 15 August, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 29 September, 45 days later.

Last spring frost	15 August
Top 7 cm of soil at 18 °C	29 September, 45 days after the last frost
Into an unheated greenhouse	8 September – 4 March; September outside: 9.6 °C at night, 21.3 °C by day; card 18–35 °C
First autumn frost	13 June, 258 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	27 November – 2 May
Days left for picking	199
Daylight	11:24 on 1 September, 12:20 on 29 September
Watering outdoors when fruiting (card)	every 5 days; the driest month, June, has 2 rainy days

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

Watermelon in Río Cuarto: care after planting

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

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

29 September — 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 Río Cuarto during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, January, averages 29.7 °C. Months that stay below 18 °C even by day on average: June (15.5 °C). Nights average below 18 °C in March–June and September–November (5.9–16.7 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
September	21.3	9.6	24	4	11:52
October	24.1	12.4	91	9	12:52
November	27.4	15.8	81	9	13:49
December	29.6	18	74	9	14:19
January	29.7	19.3	113	11	14:06
February	28.3	18.5	96	9	13:16
March	26.1	16.7	106	10	12:20
April	22.3	13.2	68	8	11:17
May	18.1	9.2	28	5	10:26
June	15.5	5.9	14	2	9:58

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Río Cuarto, Paraná is 19 days earlier and Santa Rosa 23 days later.

City	Distance	Date	Difference
San Luis	184 km	25 September – 13 March	4 days earlier
Córdoba	191 km	1 October – 5 March	2 days later
Rosario	346 km	29 September – 5 March	same day
Santa Fe	379 km	from 20 September	9 days earlier
Santa Rosa	388 km	22 October – 3 March	23 days later
Paraná	391 km	from 10 September	19 days earlier

Where to buy watermelon plants and seeds near Río Cuarto

Buy plants ready to set out from 29 September to 4 March (from 8 September to 4 March for an unheated greenhouse); seed for raising your own is sown from 11 August to 5 February. Within 15 km of Río Cuarto OpenStreetMap lists 2 garden centres, 1 plant nursery, 3 markets and 1 farm shop (collected 27 October 2026).

Vivero — plant nursery
5 km
Verdulería y despensa — market
3 km
La esquina — market
4 km
El jilguero — farm shop
7 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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