When to plant cucumbers in Chicago, Illinois
April 24 – May 8
Transplant 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. Transplant cucumbers outdoors 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
Start seeds indoors
Mar 27 – Apr 3Sow in individual pots 3–4 weeks before the outdoor window opens (UNH 3–4 weeks; Missouri G6570 3–5 weeks, sown directly in pots). Anchored to the median last spring freeze (Apr 10). University of New Hampshire Extension · University of Missouri Extension
Transplant outdoors
Apr 24 – May 8UNH allows setting out 1–2 weeks after frost; Purdue's very-tender class (at least 2 weeks after) is the more conservative and is used. Anchored to the median last spring freeze (Apr 10). Purdue University Extension · University of New Hampshire Extension
Direct-sow outdoors
Apr 24 – May 8Purdue: very tender — sow at least two weeks after the average last frost (UNH adds: when soil reaches 70°F). Penn State's earliest sowing (May 11 for a May 1 frost) is slightly earlier; the later Purdue rule is used. Anchored to the median last spring freeze (Apr 10). Purdue University Extension · Penn State Extension (York County Master Gardeners)
Variety assumption: Assumes an average slicing variety (about 55–70 days from seed; Penn State lists 70).
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 (4)
- 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.
- University of Missouri Extension: Starting Plants Indoors from Seeds (G6570) (accessed 2026-07-24)Weeks needed to grow vegetable transplants indoors (Table 2).
- 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.
- Penn State Extension (York County Master Gardeners): Vegetable Seed Planting Guide (accessed 2026-07-24)Earliest/latest sowing dates for a May 1 last-frost / Oct 1 first-frost baseline; offsets derived by date difference from May 1. Also days-to-maturity figures.