What Grows in Rock Island, Illinois

The last hard freeze (28°F) in Rock Island typically lands around Apr 7, per NOAA 1991–2020 climate normals — earlier than the light-frost dates most charts quote. That marks the hard freeze, not the last light frost — lighter frosts keep biting past it, which is why tender transplants here wait until about Apr 28.

The first hard freeze (28°F) in Rock Island typically arrives around Oct 31, per NOAA 1991–2020 climate normals — the point tender summer crops finish. Lighter frosts run ahead of it, near Oct 17, so the watching starts about Oct 1 — about 207 days after the spring freeze cleared.

Measured between 28°F hard freezes, Rock Island sees about 207 frost-free days — roughly Apr 7 through Oct 31, per NOAA 1991–2020 climate normals. Tender crops work a shorter one: nearer Apr 28 to Oct 17, about 172 days.

The federal record around Rock Island is a meaningful one — 1,293 documented sites, mostly Underground Storage Tanks entries (758), the nearest Brownfields record about 0.2 miles out — so a soil test before new food beds is a sensible precaution here, not a reason to hold back from growing. Remember that proximity to a documented site is information, not a diagnosis of any one yard; the contamination map shows exactly what sits where.

From about Oct 1 the job here turns from planting to protecting — the last start even a 30-day crop can finish. As the season closes around the first 28°F hard freeze near Oct 31 (NOAA 1991–2020 climate normals), three moves buy time: row cover or an old sheet over tender plants on still, clear nights; water the soil the afternoon before a freeze, so it holds warmth overnight; and harvest tomatoes, peppers and basil before Oct 31. Hardy greens and roots shrug off light frost and sweeten after it — leave them in.