When to plant watermelons in Invercargill: 4 December – 27 February

In Invercargill, watermelon: sow for seedlings from 16 October to 30 January; plant into a greenhouse from 13 November to 27 February; plant out into open ground from 4 December to 27 February.

Watermelon in Invercargill: soil, season and weather

In Invercargill the soil, not frost, sets the date: the last frost is over around 11 August, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 4 December, 115 days later.

Last spring frost	11 August
Top 7 cm of soil at 18 °C	4 December, 115 days after the last frost
Into an unheated greenhouse	13 November – 27 February; November outside: 9.4 °C at night, 15.9 °C by day; card 18–35 °C
First autumn frost	7 June, 186 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	1 February – 26 April
Days left for picking	127
Daylight	14:30 on 6 November, 15:35 on 4 December
Watering outdoors when fruiting (card)	every 5 days; the driest month, June, has 14 rainy days

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

Watermelon in Invercargill: care after planting

Planted on 4 December: in the first weeks water every 5 days.

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

4 December — 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 Invercargill during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, January, averages 18.4 °C. Months that stay below 18 °C even by day on average: March–June and December (10.5–17.4 °C). Nights average below 18 °C in every month of the season, from 5.1 °C to 11.9 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
December	17.4	10.9	115	18	15:46
January	18.4	11.8	115	16	15:24
February	18.4	11.9	105	14	14:00
March	17.2	10.8	97	15	12:29
April	15	9.6	111	16	10:48
May	12.9	7.7	111	17	9:23
June	10.5	5.1	93	14	8:37

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Invercargill, Christchurch is 3 days earlier and Nelson 16 days later.

City	Distance	Date	Difference
Queenstown	154 km	16 December – 8 February	12 days later
Dunedin	176 km	3 December – 10 February	1 day earlier
Timaru	318 km	19 December – 23 February	15 days later
Christchurch	464 km	1 December – 24 February	3 days earlier
Nelson	694 km	20 December – 11 March	16 days later
Blenheim	705 km	11 December – 19 February	7 days later

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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