Your place

Locations / Calgary / Sweet corn

When to plant sweet corn in Calgary

How to grow Sweet cornCalgary climate
Where are you growing?

Not realistic outdoors

Not realistic in greenhouse

Tight fit in a cold frame

Sweet corn in Calgary is doable with planning under fleece. 81 suitable days are enough for fast varieties (60 days) but not slow ones (90 days).

When to plantMay 29 – July 5

Harvest
60–90 days from seed
Season vs crop
81 grow days vs 60–90 needed
Typical frost (last spring – first fall)
May 11 – October 15

Sweet corn in Calgary is doable with planning under fleece. 81 suitable days are enough for fast varieties (60 days) but not slow ones (90 days).

Estimate. Protection varies with the cover, the weather and how you vent it.

Fleece adds about 1–4 °C on frosty nights, depending on its weight. Remove it on warm days.

Fleece also cuts light: about 5–10 % for light fleece, up to 50–70 % for heavy grades. Take it off by day once frosts are over.

Cover dates are modelled from weather-model data using published greenhouse studies. They are not measured in your greenhouse. A max–min thermometer inside will tell you more.

Typical last frost estimate range May 12 – April 16, depending on the cover and the night.

Planting conditions

Sweet corn planting activities across the year: Direct sowJFMAMJJASOND~May 11~Oct 15
  • Direct sow
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 row81
Days to harvest60–90 days from seed
May 29 – Jul 5
Direct sow
ActivityWindowNotes
Direct sowMay 29 – Jul 5Plant outdoors in this window.
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.

Protected frost and sowing dates are modelled estimates from weather-model data and published greenhouse studies, not measured in your greenhouse. A max–min thermometer inside will tell you more.

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, from modelled cover temperatures for the growing method you selected.

Sweet corn planting and growing weeks in CalgaryJANFEBMARAPRMAYJUNJULAUGSEPOCTNOVDECPlantingGrowing
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 11
Safer last spring frostMay 11
Typical first fall frostOctober 15
Safer first fall frostOctober 15
Frost-free days156
Outdoor sow dateMay 29
Direct sow windowMay 29 – July 5
Suitable growing windowMay 29 – August 17 (81 days)

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 Calgary, 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: none (0 days)

Planting window for Sweet corn: Jun 9 – Jul 3 (25 days)

Usually too cold: Aug 3 – Dec 31

Outdoors: weekly temperatures and windows

Temperatures across the year for Calgary. 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.

JanFebMarAprMayJunJulAugSepOctNovDec−50 °C−58 °F−40 °C−40 °F−30 °C−22 °F−20 °C−4 °F−10 °C14 °F0 °C32 °F10 °C50 °F20 °C68 °F30 °C86 °F40 °C104 °FTolerable 13–35 °CTolerable 55–95 °FIdeal 21–32 °CIdeal 70–90 °FWindowGrowingnonePlantingJun 9 – Jul 3Last frost ~May 12First frost ~Oct 13
  • 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 1 · Jan 1 – Jan 4

Average −13 to −4 °C · Possible −33 to 4 °C

Growing: too cold

Planting: too cold

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 Calgary

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 51.00, -114.10, 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).

Report a problem