When to plant sweet corn in Toronto

Where are you growing?

Comfortable

Comfortable in greenhouse

Comfortable in a cold frame

Sweet corn in Toronto is a good fit outdoors. The suitable growing window of 128 days covers the 60–90 days this plant usually needs.

When to plantMay 14 – July 21

Harvest: July 13 – September 18
Season vs crop: 128 grow days vs 60–90 needed
Typical frost (last spring – first fall): May 9 – October 31

Sweet corn in Toronto is a good fit outdoors. The suitable growing window of 128 days covers the 60–90 days this plant usually needs.

Planting conditions

Direct sow
Harvest

Local activity windows for this place and growing method. Blue fill is usually too cold for this plant. Dashed lines are typical last and first frost.

Suitable growing days in a row128

Days to harvest60–90 days from seed

May 14 – Jul 21

Direct sow

Jul 13 – Sep 18

Harvest

Activity	Window	Notes
Direct sow	May 14 – Jul 21	Plant outdoors in this window.
Harvest	Jul 13 – Sep 18	Expected harvest from typical days to harvest.

Blue fill is usually too cold for this plant. Dashed lines are typical last and first frost. Adjust a week or two for your conditions.

Planting and growing across the year

Planting is the sow / plant-out window. Growing is daytime air versus this plant’s ideal (21 – 32 °C) and tolerable (13 – 35 °C) ranges.

Planting uses sow / plant-out rules (frost, soil germination, night, and last-sow): green when plantable, blue diagonal when nights or soil are too cold, amber cross-hatch when too hot, faint for other calendar limits. Growing shows daytime air against this plant’s ideal and tolerable ranges across the year.

Key dates

Typical last spring frostMay 9

Safer last spring frostMay 9

Typical first fall frostOctober 31

Safer first fall frostOctober 31

Frost-free days174

Outdoor sow dateMay 14

Direct sow windowMay 14 – July 21

Suitable growing windowMay 14 – September 18 (128 days)

Expected harvestJuly 13 – September 18

How these dates are judged

Ideal conditions: Daytime air from 21 – 32 °C.
Suitable conditions: Daytime air from 13 – 35 °C.
Last frost and first frost: Typical spring and fall frost dates for Toronto, shown in the key dates.
Days to harvest: 60–90 days from seed, from typical days to harvest.
Sowing window: Dated sow and harvest bars use frost dates, soil minima, night limits, and last-sow count-back from typical crop timing. The year strip and weekly chart use the same window: air ratings only colour weeks inside it.

Growing window for Sweet corn: May 14 – Sep 18 (128 days)

Planting window for Sweet corn: May 14 – Jul 21 (69 days)

Usually too cold: Jan 1 – May 10; Oct 5 – Dec 31

Outdoors: weekly temperatures and windows

Temperatures across the year for Toronto. Shaded bands are this plant’s ideal and tolerable daytime air ranges. Growing is daytime air suitability; Planting is sow / plant-out conditions (same colour language). Window brackets mark each stretch.

Ideal range
Tolerable range
Possible min to max
Average min to max
Suitable
Tolerable
Too cold
Too hot

Selected week · tap a week or use the arrows

Week 20 · May 11 – May 17

Average 8 to 16 °C · Possible 0 to 24 °C

Growing: too cold (inside window)

Planting: suitable

A week is in range when its average low and high sit inside the tolerance band 13 to 35 °C; it is suitable when that average range also overlaps the ideal 21 to 32 °C band and possible readings stay within 0 °C to 35 °C. Crossing a possible limit, or missing the ideal band, makes it tolerable; any chance of frost (possible low below 0 °C) makes it too cold. When a sowing window is calculated, weeks outside that window are uncoloured even if air is in range.

Based on average frost dates.

Show all 53 weeks

Cover method weekly charts

Outdoor weekly chart is above. Open a cover chart only if you grow under fleece, a cold frame, or an unheated greenhouse.

Other plants for Toronto

Calculated by Plan & Plant · Method · Data 2019–2026

Frost and suitability dates are typical figures from climate statistics. Microclimates vary; they are not a guarantee.

How we calculated this

Data: ERA5-Land via Open-Meteo, cell 43.70, -79.40, years 2019–2026 (not a 30-year climate normal yet).
Typical and safer dates: Typical last frost is the date after which half of winters in this sample had no more frost; safer is later in the sample so fewer winters still frosted.
Crop rule: Local windows for Sweet corn from frost dates, temperature ratings, and crop timing rules.
Confidence: Provisional — short or thin sample for this place.
Full methodology (algorithm 2026-10-season-6).

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