When to plant watermelons in Idaho Falls: 4 June – 5 July

In Idaho Falls, watermelon: sow for seedlings from 16 April to 7 June; plant into a greenhouse from 14 May to 5 July; plant out into open ground from 4 June to 5 July. For plants and seeds, the places nearby include Town and Country Gardens (garden centre, 7 km) and R & D Wholesale Nursery (garden centre, 8 km); addresses and opening hours are below.

Watermelon in Idaho Falls: soil, season and weather

In Idaho Falls the soil, not frost, sets the date: the last frost is over around 11 May, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 4 June, 24 days later.

Last spring frost	11 May
Top 7 cm of soil at 18 °C	4 June, 24 days after the last frost
Into an unheated greenhouse	14 May – 5 July; May outside: 5.5 °C at night, 20.6 °C by day; card 18–35 °C
First autumn frost	14 October, 132 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	2 August – 2 September
Days left for picking	73
Daylight	14:23 on 7 May, 15:15 on 4 June
Watering outdoors when fruiting (card)	every 5 days; the driest month, July, has 1 rainy day

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

Watermelon in Idaho Falls: care after planting

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

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

4 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 Idaho Falls during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, July, averages 32.9 °C. Months that stay below 18 °C even by day on average: October (15.3 °C). Nights average below 18 °C in every month of the season, from 2.4 °C to 15.7 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
June	27.3	11.2	21	5	15:24
July	32.9	15.7	5	1	15:07
August	30.9	14.2	14	3	14:00
September	25.2	9.5	27	5	12:33
October	15.3	2.4	36	7	11:05

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Idaho Falls, Boise is 28 days earlier and Helena 29 days later.

City	Distance	Date	Difference
Salt Lake City	305 km	19 May – 17 July	16 days earlier
Boise	336 km	7 May – 18 July	28 days earlier
Helena	345 km	3 July – 5 August	29 days later
Billings	377 km	2 June – 5 July	2 days earlier
Missoula	406 km	30 June – 8 August	26 days later
Elko	425 km	20 May – 4 July	15 days earlier

Where to buy watermelon plants and seeds near Idaho Falls

Buy plants ready to set out from 4 June to 5 July (from 14 May to 5 July for an unheated greenhouse); seed for raising your own is sown from 16 April to 7 June. Within 15 km of Idaho Falls OpenStreetMap lists 4 garden centres, 3 farm-supply shops, 2 plant nurseries, 2 markets and 1 farm shop (collected 28 October 2026).

Town and Country Gardens — garden centre
South Yellowstone Highway 5800, 83402 Idaho Falls · 7 km · tcgardens.com
R & D Wholesale Nursery — garden centre
West Heritage Circle 2312, 83402 Idaho Falls · 8 km
Siems Enterprises LLC — farm supply
Mon, Thu, Fri 08:00–17:00; Tue 08:00–16:15; Wed 08:00–15:00; Sat 09:00–12:00 · 15 km
Itty Bitty Farms — farm shop
East Lincoln Road 5229, 83401-5769 Idaho Falls · 8 km · ittybittyfarmstore.com

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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