When to plant watermelons in Boise: 7 May – 18 July

In Boise, watermelon: sow for seedlings from 19 March to 20 June; plant into a greenhouse from 16 April to 18 July; plant out into open ground from 7 May to 18 July. For plants and seeds, the places nearby include Zamzows (farm supply, 8 km) and Cloverdale Nursery (garden centre, 11 km); addresses and opening hours are below.

Watermelon in Boise: soil, season and weather

In Boise 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 7 May, 22 days later.

Last spring frost	15 April
Top 7 cm of soil at 18 °C	7 May, 22 days after the last frost
Into an unheated greenhouse	16 April – 18 July; April outside: 4.5 °C at night, 17.6 °C by day; card 18–35 °C
First autumn frost	27 October, 173 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	5 July – 15 September
Days left for picking	114
Daylight	13:07 on 9 April, 14:23 on 7 May
Watering outdoors when fruiting (card)	every 5 days; the driest month, July, has 1 rainy day

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

Watermelon in Boise: care after planting

Planted on 7 May: in the first weeks water every 5 days.

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

7 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 Boise during the watermelon season

Days average above the watermelon card's 18–35 °C in July (35.1 °C). Nights average below 18 °C in May, June and September, October (6.3–13.9 °C).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
May	23	9.1	42	8	14:42
June	29	13.9	22	4	15:25
July	35.1	19.2	3	1	15:08
August	33.7	18.1	6	1	14:01
September	27.9	13.1	12	3	12:33
October	18.2	6.3	26	5	11:05

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

All the nearest cities on our list plant watermelon later than Boise; the closest date is in Salt Lake City, 12 days later.

City	Distance	Date	Difference
Elko	310 km	20 May – 4 July	13 days later
Idaho Falls	336 km	4 June – 5 July	28 days later
Missoula	400 km	30 June – 8 August	54 days later
Spokane	460 km	22 May – 6 July	15 days later
Helena	466 km	3 July – 5 August	57 days later
Salt Lake City	476 km	19 May – 17 July	12 days later

Where to buy watermelon plants and seeds near Boise

Buy plants ready to set out from 7 May to 18 July (from 16 April to 18 July for an unheated greenhouse); seed for raising your own is sown from 19 March to 20 June. Within 15 km of Boise OpenStreetMap lists 4 garden centres, 2 farm-supply shops and 1 plant nursery (collected 20 October 2026).

Cloverdale Nursery — garden centre
North Cloverdale Road 2528, 83713 Boise · 11 km
Madeline George Garden Design & Nursery — plant nursery
West Hill Road Parkway 10550, 83714 Boise · 13 km · madelinegeorge.com
Zamzows — farm supply
East Overland Road 3650, 83642 Meridian · 12 km
Zamzows — farm supply
West State Street 6208, 83703 Boise · 8 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