When to plant watermelons in Missoula: 30 June – 8 August

In Missoula, watermelon: sow for seedlings from 12 May to 11 July; plant into a greenhouse from 9 June to 8 August; plant out into open ground from 30 June to 8 August.

Watermelon in Missoula: soil, season and weather

In Missoula the soil, not frost, sets the date: the last frost is over around 18 May, but the top 7 cm of soil reaches 18 °C — the minimum on the watermelon card — only around 30 June, 43 days later. 98 days separate planting out (30 June) from the first autumn frost (6 October); the card's 59 days to the first harvest leave 39 for picking, so a start 5 weeks late would still fit.

Last spring frost	18 May
Top 7 cm of soil at 18 °C	30 June, 43 days after the last frost
Into an unheated greenhouse	9 June – 8 August; June outside: 8.4 °C at night, 22.1 °C by day; card 18–35 °C
First autumn frost	6 October, 98 days after the start
Days in the bed to the first harvest (card)	59
First harvest, if planted in this window	28 August – 6 October
Days left for picking	39
Daylight	15:38 on 2 June, 15:50 on 30 June
Watering outdoors when fruiting (card)	every 5 days; the driest month, July, has 4 rainy days

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

Watermelon in Missoula: care after planting

Planted on 30 June: in the first weeks water every 5 days.

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

30 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 Missoula during the watermelon season

No month of the season averages above the watermelon card's 18–35 °C by day; the warmest, July, averages 28.3 °C. Months that stay below 18 °C even by day on average: October (12.6 °C). Nights average below 18 °C in every month of the season, from 1.5 °C to 12.9 °C.

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
June	22.1	8.4	63	10	15:51
July	28.3	12.9	11	4	15:32
August	27.3	12.1	21	4	14:15
September	21.6	7.7	42	6	12:37
October	12.6	1.5	58	11	10:57

ERA5 2016–2025, Open-Meteo

Watermelon in nearby cities

Around Missoula, Boise is 54 days earlier and Helena 3 days later.

City	Distance	Date	Difference
Helena	155 km	3 July – 5 August	3 days later
Spokane	271 km	22 May – 6 July	39 days earlier
Boise	400 km	7 May – 18 July	54 days earlier
Idaho Falls	406 km	4 June – 5 July	26 days earlier
Billings	441 km	2 June – 5 July	28 days earlier
Calgary	465 km	18 June – 22 June	12 days earlier

Where to buy watermelon plants and seeds near Missoula

Buy plants ready to set out from 30 June to 8 August (from 9 June to 8 August for an unheated greenhouse); seed for raising your own is sown from 12 May to 11 July. Within 15 km of Missoula OpenStreetMap lists 3 garden centres, 1 farm-supply shop, 2 plant nurseries, 2 markets and 6 farm shops (collected 28 October 2026).

Farm Hand Farm — farm shop
3 km
Harvest Calling Farms — farm shop
4 km
Hickory Leaf Dairy Goats — farm shop
4 km
Target Range Farmer's Market — farm shop
5 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