When to plant zucchini in Thunder Bay: 8 July – 6 August

In Thunder Bay, zucchini: sow for seedlings from 27 May to 16 July; plant into a greenhouse from 17 June to 6 August; plant out into open ground from 8 July to 6 August.

Zucchini in Thunder Bay: soil, season and weather

In Thunder Bay 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 zucchini card — only around 8 July, 58 days later.

Last spring frost	11 May
Top 7 cm of soil at 18 °C	8 July, 58 days after the last frost
First autumn frost	23 October, 107 days after the start
Days in the bed to the first harvest (card)	36
First harvest, if planted in this window	13 August – 11 September
Days left for picking	71
Daylight	16:06 on 17 June, 15:55 on 8 July
Watering outdoors when fruiting (card)	every 3 days; the driest month, August, has 11 rainy days

The same dates in Thunder Bay hold for Cucumber, Bell Pepper, Eggplant, Pumpkin and Watermelon.

Zucchini in Thunder Bay: care after planting

Planted on 8 July: in the first weeks water every 4 days.

Pests and diseases of zucchini to watch for:

Weather in Thunder Bay during the zucchini season

About 294 mm of rain falls in the season; August is the driest month (63 mm) and September the wettest (86 mm).

Month	Day, °C	Night, °C	Rain, mm	Rainy days	Daylight on the 15th
July	23.6	14.4	74	11	15:44
August	22.3	14.2	63	11	14:23
September	18.2	10.9	86	11	12:38
October	10.5	4.2	71	10	10:54

ERA5 2016–2025, Open-Meteo

Zucchini in nearby cities

All the nearest cities on our list plant zucchini earlier than Thunder Bay; the closest date is in Duluth, 10 days earlier.

City	Distance	Date	Difference
Duluth	279 km	28 June – 11 August	10 days earlier
Green Bay	439 km	27 May – 13 August	42 days earlier
Minneapolis	487 km	28 May – 7 August	41 days earlier
Traverse City	488 km	5 June – 23 August	33 days earlier
Grand Forks	584 km	5 June – 30 July	33 days earlier
Fargo	589 km	31 May – 30 July	38 days earlier

Where to buy zucchini plants and seeds near Thunder Bay

Buy plants ready to set out from 8 July to 6 August (from 17 June to 6 August for an unheated greenhouse); seed for raising your own is sown from 27 May to 16 July. Within 15 km of Thunder Bay OpenStreetMap lists 2 garden centres and 1 market (collected 20 October 2026).

Goods & Co. — market
Red River Road 251 · 7 km · goodscomarket.ca
Trevisanutto's Garden Centre — garden centre
7 km
Creekside Nursery — garden centre
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.

Questions