Dunlap, IL planting calendar
- USDA zone
- 5b−15 to −10 °F
- Last frost
- Apr 22avg, 32°F
- First frost
- Oct 14avg, 32°F
- Growing season
- 174days
Dunlap, Illinois is in USDA plant hardiness zone 5b. Its average last spring frost is around April 22 and the first fall frost around October 14, giving a growing season of about 174 days (NOAA 1991–2020 normals, 32°F, median). Start tender crops like tomatoes and peppers indoors weeks before the last frost and set them out afterward; sow hardy crops such as peas, spinach, and lettuce before it. The planner below turns those frost dates into a printable per-crop planting calendar.
Dunlap planting calendar
Each crop's windows are counted from Dunlap's average frost dates. 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.
- Start indoors
- Plant out
- Fall sowing
- First harvest
| Crop | Frost tolerance | Start indoors | Plant out | First harvest | Fall planting |
|---|---|---|---|---|---|
| Tomato | Tender | Feb 25 – Mar 11 | Apr 29 – May 6 | Jun 28 – Jul 18 | — |
| Pepper | Very tender | Feb 11 – Feb 25 | May 6 – May 13 | Jul 5 – Aug 4 | — |
| Cucumber | Tender | Mar 25 – Apr 1 | Apr 29 – May 6 | Jun 18 – Jul 8 | — |
| Summer squash / zucchini | Tender | — | Apr 29 – May 6 | Jun 13 – Jun 28 | — |
| Bush bean | Tender | — | Apr 29 – May 6 | Jun 18 – Jun 28 | Aug 15 – Aug 25 |
| Sweet corn | Tender | — | Apr 22 – May 6 | Jun 21 – Jul 21 | — |
| Basil | Very tender | Mar 11 – Mar 25 | Apr 29 – May 6 | May 29 – Jun 13 | — |
| Lettuce | Half-hardy | Mar 11 – Mar 25 | Mar 25 – Apr 8 | May 9 – May 24 | Aug 1 – Aug 16 |
| Pea | Hardy | — | Mar 11 – Mar 25 | May 5 – May 20 | Jul 22 – Aug 6 |
| Spinach | Hardy | — | Mar 11 – Mar 25 | Apr 20 – Apr 30 | Aug 11 – Aug 21 |
| Carrot | Half-hardy | — | Apr 1 – Apr 8 | May 31 – Jun 20 | Jul 12 – Aug 1 |
| Broccoli | Half-hardy | Feb 25 – Mar 11 | Mar 25 – Apr 8 | May 19 – Jun 8 | Jul 17 – Aug 6 |
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.
Frost & freeze dates
From NOAA's 1991–2020 Climate Normals at station USC00117004. 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 (p10 for spring, p90 for fall) — 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 | May 2 | May 16 | Oct 4 | Oct 17 | 155 |
| 32°F (freeze) | Apr 22 | May 6 | Oct 14 | Oct 27 | 174 |
| 28°F | Apr 12 | Apr 30 | Oct 26 | Nov 7 | 197 |
| 24°F | Apr 2 | Apr 19 | Nov 4 | Nov 19 | 217 |
32°F is the standard "freeze" line that damages tender crops; lighter 36°F frost can nip the most cold-sensitive plants, while hardy crops shrug off light frost down toward 28°F. Use the threshold that matches what you are protecting.
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. Warm-season crops need a long, warm GDD total; a short, cool GDD total favors greens and brassicas.
| Model | °F·days | Used for |
|---|---|---|
| Base 50°F (warm-season) | 3,345 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 5,551 | cool-season crops (brassicas, greens) |
Hardiness zone 5b
Dunlap sits in USDA plant hardiness zone 5b on the 2023 map — meaning its average annual extreme minimum winter temperature is about −15 to −10 °F. That number 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.
Explore more places in zone 5b, or see all USDA hardiness zones.
Frequently asked questions
- What USDA hardiness zone is Dunlap?
- Dunlap, Illinois is in USDA plant hardiness zone 5b on the 2023 map (average annual extreme minimum temperature −15 to −10 °F) — from the USDA Plant Hardiness Zone Map 2023, matched to this location's ZIP. See the methodology page for sources.
- When is the last frost in Dunlap?
- The average (median) last spring frost at 32°F is around April 22, from NOAA's 1991–2020 climate normals at the nearest reporting station. Roughly one year in ten the last frost is as late as May 6, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in Dunlap?
- The average first fall frost at 32°F is around October 14. That leaves a growing season of about 174 days between the average last spring and first fall frosts.
- When should I start tomatoes in Dunlap?
- Start tomato seeds indoors about Feb 25 – Mar 11 and transplant them outside about Apr 29 – May 6, once the danger of frost has passed. Estimated first harvest is around Jun 28 – Jul 18.
- How long is the growing season in Dunlap?
- About 174 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~April 22) and the average first fall frost (~October 14). Cold-hardy crops extend usable time at both ends; frost-tender crops fit inside it.
Sources & method
Frost, freeze, growing-season, and growing-degree-day figures are NOAA NCEI U.S. Climate Normals 1991–2020 for station USC00117004 (Princeville, 2.1 km away). The hardiness zone is the USDA Plant Hardiness Zone Map 2023, matched to this 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.