First & Last Frost Dates in Illinois (2026)
Typical first freeze October 16 · last spring frost April 26 · about 175 growing days between them.
First frost approaching — typically 18 days outWhere Illinois sits on the frost line
NOAA 1991 to 2020 normalsChicago's urban heat island plus Lake Michigan pushes the city's first frost past mid-October — collar-county gardens freeze noticeably earlier.
Frost dates for your exact ZIP
The dates above are the state median. Enter a ZIP code to snap to the nearest of 150 NOAA reference stations and read that station’s own first and last freeze instead:
Frost dates across Illinois
State averages hide huge local spread — elevation, cold-air drainage, urban heat, and nearby water routinely move frost dates by two to four weeks within the same state. Median dates for representative Illinois stations:
| City | Typical first frost | Typical last frost |
|---|---|---|
| Chicago | October 24 | April 20 |
| Springfield | October 16 | April 16 |
| Carbondale | October 24 | April 8 |
Not near these cities? The ZIP lookup above snaps any US address to its nearest reference station. It is the same tool as the site’s national frost date lookup.
Your Illinois first-frost playbook
The Illinois planting calendar
Every date below is computed from Illinois’s own frost anchors — last frost ~April 26, first frost ~October 16 — using the standard week-count rules seed packets assume. Shift everything a few days for your microclimate (see the city table above).
| Garden task | Typical Illinois date | The rule it comes from |
|---|---|---|
| Start onions & leeks indoors | February 15 | ~10 weeks before last frost |
| Start peppers & tomatoes indoors | March 1 | ~8 weeks before last frost |
| Direct-sow peas & spinach | March 22 | ~5 weeks before last frost |
| Plant potatoes | April 12 | ~2 weeks before last frost |
| Transplant tomatoes & peppers out | May 19 | ~1 week after the late frost date |
| Sow fall carrots (70-day) | July 23 | ~12 weeks before first frost |
| Sow fall spinach & lettuce | August 27 | ~7 weeks before first frost |
| Plant garlic | October 30 | ~2 weeks after first frost |
Two rules do most of the work: count backward from first frost for fall crops (a 70-day carrot needs sowing ~12 weeks out, because fall growth slows as days shorten), and count forward from the late last-frost date — not the median — for anything frost-tender going outside.
What dies at what temperature
“Frost” isn’t one event. Surfaces can frost with air temps as high as 36–37°F on calm clear nights; a freeze is 32°F; a hard freeze is 28°F and ends the season for anything unprotected. Crops check out at very different points along the way:
| Crops | Damage point | What it means |
|---|---|---|
| Basil, impatiens, coleus, sweet potato vine | 38–40°F | Damaged before an official frost even hits |
| Tomatoes, peppers, cucumbers, squash, beans | 32°F | Killed by the first light freeze |
| Lettuce, chard, cilantro, peas | 28°F | Shrug off light frost; done at a hard freeze |
| Broccoli, cabbage, carrots, beets | 25°F | Keep producing weeks past first frost |
| Kale, spinach, Brussels sprouts, parsnips | 15–20°F | Frost makes them sweeter — harvest all late fall |
The practical read for Illinois: once you’re inside the October 2–October 31 window, the top two rows are living on borrowed time — while the bottom two rows are just getting started. Frost converts starches to sugars in kale, carrots, and parsnips; the sweetest harvests of the year come after first frost.
Illinois frost date FAQ
Plan the rest of the season
More Midwest frost dates
Dates are median first/last 32°F freeze approximations from NOAA 1991–2020 climate normals for representative stations, bracketed by roughly the 10%/90% range. Any single year varies; microclimates vary more. National picture: first frost dates for every state