USDA zone 7a in Illinois
USDA plant hardiness zone 7a covers 16 locations across Illinois (average annual extreme minimum 0 to 5 °F): Anna, IL, Belleville, IL, Belleville, IL, Benton, IL, Cairo, IL, Carbondale, IL, and 10 more. Average last spring frost across this group ranges April 2 (Cairo) to April 19 (Rosiclare), and growing seasons run 181–216 days (Rosiclare to Olmsted) — even within one state, because hardiness sets winter survival, not planting dates. The table below gives every Illinois location's own frost dates; the printable planting calendar uses Belleville, this group's median-season location.
- USDA zone
- 7a0 to 5 °F
- Last frost range
- Apr 2–Apr 19avg, 32°F
- First frost range
- Oct 19–Nov 5avg, 32°F
- Growing season range
- 181–216days
Locations in this group
Every location below shares this zone and a nearby weather station, but keeps its own frost dates — find your town for its own numbers, or use the ZIP planner on the home page for an instant personalized answer.
| Location | Also covers | Nearest station | Last frost | First frost | Season (days) |
|---|---|---|---|---|---|
| Anna | Jonesboro, Alto Pass, Cobden, Buncombe, Dongola, Mill Creek | Anna 2 Nne | Apr 8 | Oct 29 | 203 |
| Belleville * | Cahokia Heights, East St. Louis, Dupo, Millstadt, Washington Park | Cahokia St Louis Ap | Apr 8 | Oct 26 | 200 |
| Belleville | O'Fallon, Collinsville, Fairview Heights, Caseyville, Freeburg, Maryville, +6 more | Belleville Siu Rsch | Apr 12 | Oct 20 | 189 |
| Benton | — | Benton 2 N | Apr 4 | Oct 28 | 206 |
| Cairo | Mounds, Unity, Mound, Barlow | Cairo 3n | Apr 2 | Oct 31 | 211 |
| Carbondale | Marion, Herrin, Makanda, Goreville, Johnston, Crainville, +4 more | Carbondale Sewage Plt | Apr 9 | Oct 22 | 195 |
| Carmi | Grayville, Broughton, Norris, Ridgway, Omaha, Crossville, +2 more | Carmi 3 | Apr 15 | Oct 19 | 183 |
| Chester | Ste. Genevieve, Red Bud, Evansville, Prairie du Rocher, Ellis Grove | Kaskaskia Rvr Navigation Lock | Apr 8 | Oct 30 | 202 |
| Du Quoin | West Frankfort, Pinckneyville, North, Christopher, Zeigler, Valier, +7 more | Du Quoin 4 Se | Apr 6 | Oct 22 | 199 |
| Harrisburg | Eldorado, Pittsburg, Raleigh, Galatia, Carrier Mills, Equality, +1 more | Harrisburg | Apr 7 | Oct 26 | 202 |
| Metropolis | Farley, Symsonia | Brookport Dam 52 | Apr 6 | Oct 27 | 203 |
| Murphysboro | Alto Pass, Grand Tower, Gorham, Ava, De Soto, Hurst | Carbondale Southern Il Ap | Apr 9 | Oct 22 | 195 |
| Olmsted | Ullin, Karnak, Pulaski, New Grand Chain, Cypress | Grand Chain Dam 53 | Apr 3 | Nov 5 | 216 |
| Rosiclare | Junction, Elizabethtown, Cave-In-Rock, Eddyville | Rosiclare 5nw | Apr 19 | Oct 20 | 181 |
| Sparta | Steeleville, Percy, Tilden, Baldwin, Cutler, Campbell Hill, +2 more | Sparta 1 W | Apr 12 | Oct 22 | 191 |
| Vienna | Stonefort, Belknap, New Burnside, Creal Springs, Simpson, Golconda, +1 more | Dixon Springs Agric Ctr | Apr 14 | Oct 21 | 189 |
* Belleville is this group's median-season location — the calendar below is computed from its data.
Data: NOAA NCEI U.S. Climate Normals 1991–2020 (public domain) and USDA Plant Hardiness Zone Map 2023. Planting windows synthesized from U.S. Cooperative Extension guides.
Planting calendar (Belleville, representative)
Computed from Belleville's average frost dates — the median-season location in this Illinoiszone 7a group. hatched = start seeds indoors, solid green = plant out, teal = a fall sowing, and the terracotta dot marks the estimated first harvest. Ranges are extension-guide planning guidance, not guarantees — your own location's dates may run a week or two earlier or later (see the table above).
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting | Season fit |
|---|---|---|---|---|---|---|
| Tomato | Tender | Feb 11 – Feb 25 | Apr 15 – Apr 22 | Jun 14 – Jul 4 | — | matures comfortably |
| Pepper | Very tender | Jan 28 – Feb 11 | Apr 22 – Apr 29 | Jun 21 – Jul 21 | — | matures comfortably |
| Cucumber | Tender | Mar 11 – Mar 18 | Apr 15 – Apr 22 | Jun 4 – Jun 24 | — | matures comfortably |
| Summer squash / zucchini | Tender | — | Apr 15 – Apr 22 | May 30 – Jun 14 | — | matures comfortably |
| Bush bean | Tender | — | Apr 15 – Apr 22 | Jun 4 – Jun 14 | Aug 27 – Sep 6 | matures comfortably |
| Sweet corn | Tender | — | Apr 8 – Apr 22 | Jun 7 – Jul 7 | — | matures comfortably |
| Basil | Very tender | Feb 25 – Mar 11 | Apr 15 – Apr 22 | May 15 – May 30 | — | matures comfortably |
| Lettuce | Half-hardy | Feb 25 – Mar 11 | Mar 11 – Mar 25 | Apr 25 – May 10 | Aug 13 – Aug 28 | matures comfortably |
| Pea | Hardy | — | Feb 25 – Mar 11 | Apr 21 – May 6 | Aug 3 – Aug 18 | matures comfortably |
| Spinach | Hardy | — | Feb 25 – Mar 11 | Apr 6 – Apr 16 | Aug 23 – Sep 2 | matures comfortably |
| Carrot | Half-hardy | — | Mar 18 – Mar 25 | May 17 – Jun 6 | Jul 24 – Aug 13 | matures comfortably |
| Broccoli | Half-hardy | Feb 11 – Feb 25 | Mar 11 – Mar 25 | May 5 – May 25 | Jul 29 – Aug 18 | matures comfortably |
Which crops fit this growing season
Using Belleville's own 200-day growing season (32°F, NOAA 1991–2020 median) against each crop's real days-to-maturity range: 12 of 12 crops mature here with comfortable margin. A different location in the table above with a longer or shorter season will get a different mix — the ZIP planner on the home page gives your own.
Frost & freeze dates (Belleville)
From NOAA's 1991–2020 Climate Normals at station USW00003960. The median (p50) is the average date; the 90%-safe column is the date the freeze has passed in about 9 years out of 10 — the conservative date to plant after or harvest before.
| Threshold | Last spring — avg | Last spring — 90%-safe | First fall — avg | First fall — 90%-safe | Season (days) |
|---|---|---|---|---|---|
| 36°F | Apr 19 | May 4 | Oct 17 | Oct 28 | 178 |
| 32°F (freeze) | Apr 8 | Apr 23 | Oct 26 | Nov 7 | 200 |
| 28°F | Mar 28 | Apr 12 | Nov 6 | Nov 24 | 224 |
| 24°F | Mar 14 | Mar 31 | Nov 18 | Dec 6 | 250 |
Growing degree days
Growing degree days (GDD) accumulate warmth above a base temperature over the year — a better predictor of crop development than the calendar alone. This group's median GDD (base 50°F) across all 16 locations is 4,246; Belleville's own reading is shown below.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 4,263 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 6,808 | cool-season crops (brassicas, greens) |
Hardiness zone 7a in Illinois
Zone 7a means an average annual extreme minimum winter temperature of about 0 to 5 °F on the USDA's 2023 map — the number that tells you which perennials, shrubs, and trees reliably survive an average winter here. It does not set your planting dates, which come from the frost calendar above. Illinois spans 5 hardiness zones in this dataset — see all Illinois locations for the full range, including zones5a, 5b, 6a, 6b.
Explore zone 7a in other states at zone 7a, or see all USDA hardiness zones.
Frequently asked questions
- What does USDA hardiness zone 7a mean in Illinois?
- Zone 7a means an average annual extreme minimum winter temperature of 0 to 5 °F — the standard USDA measure of which perennials survive winter. 16 locations in Illinois fall in this zone. It does not set planting dates; see the frost calendar below for that.
- Where in Illinois's zone 7a is the growing season longest?
- Olmsted runs the longest season on this page at about 216 days; Rosiclare is shortest at about 181 days — they share the same hardiness zone, but they sit at different weather stations, so their frost calendars differ.
- When should I plant tomatoes in Illinois's zone 7a?
- Using Belleville's frost dates (this page's median-season location): start seeds indoors about Feb 11 – Feb 25, then transplant outside about Apr 15 – Apr 22. Your own location in the table above may differ by a week or two — use the ZIP planner on the home page for your exact station's dates.
- Does every location in Illinois's zone 7a have the same frost dates?
- No — they do not all share a weather station, so frost dates vary by a week or more across the 16 locations listed (see the table above for each location's own dates).
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020, one reading per location's own nearest station (see the table above). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to each location's ZIP. Planting windows are computed by counting from the average last and first frost using per-crop offsets synthesized from U.S. Cooperative Extension guides — the full method and citations are on the methodology page.