When to plant sweet corn in Chicago, Illinois
April 24 – May 8
Direct-sow outdoors · typical Chicago yearClimate basis: NOAA station Chicago Northerly Is, IL (USC00111550), 2 mi (3 km) from downtown Chicago (ZCTA 60602 centroid), elevation 583 ft, on the 1991–2020 climate normals. Direct-sow sweet corn from approximately the dates above, anchored to the median last spring 32°F freeze (April 10). One year in ten still freezes after April 25.
The Chicago year
- indoors under lights
- in the garden
- frost-free season
- 1-in-10 years still freeze to Apr 25
Every method, with its sources
Direct-sow outdoors
Apr 24 – May 8UGA: wait until at least two weeks after the last average killing frost. Purdue lists corn as tender (after last frost) and UNH keys sowing to 60°F soil; the later UGA rule is used. Anchored to the median last spring freeze (Apr 10). University of Georgia Cooperative Extension · Purdue University Extension · University of New Hampshire Extension
Start seeds indoors
Not calculatedThe cited guides time sweet corn by direct seeding only.
Transplant outdoors
Not calculatedThe cited extension guides do not time an outdoor transplanting window for this crop.
Fall planting
Not calculatedNo source-backed fall planting rule exists for this crop in the registry, so no fall window is calculated.
Variety assumption: Assumes a mid-season hybrid (about 70–85 days; Penn State lists 80).
These windows describe typical years (1991–2020 climate normals), not this year's forecast. Freezes happen outside them — especially in frost pockets, valleys, and urban edges. Watch the forecast before committing tender plants.
Crop rule sources (3)
- University of Georgia Cooperative Extension: Growing Home Garden Sweet Corn (Circular 905) (accessed 2026-07-24)"Wait until at least two weeks after the last average killing frost before planting."
- Purdue University Extension: Indiana Vegetable Planting Calendar (HO-186-W) (accessed 2026-07-24)Hardiness classes: hardy = plant 4-6 wk before last spring frost; semi-hardy = 2-4 wk before; tender = after average last frost; very tender = at least 2 wk after. Table 2: fall planting at least 4-8 wk before first fall frost.
- University of New Hampshire Extension: Growing Vegetables: When to Plant Your Vegetable Garden [fact sheet] (accessed 2026-07-24)Per-crop 'time from seed to transplant' and 'safe to set out in garden' relative to last frost.