Roselle, IL planting calendar
- USDA zone
- 5b−15 to −10 °F
- Last frost
- Apr 16avg, 32°F
- First frost
- Oct 28avg, 32°F
- Growing season
- 193days
Roselle, Illinois is in USDA plant hardiness zone 5b. Its average last spring frost is around April 16 and the first fall frost around October 28, giving a growing season of about 193 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.
Roselle planting calendar
Each crop's windows are counted from Roselle'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 19 – Mar 5 | Apr 23 – Apr 30 | Jun 22 – Jul 12 | — |
| Pepper | Very tender | Feb 5 – Feb 19 | Apr 30 – May 7 | Jun 29 – Jul 29 | — |
| Cucumber | Tender | Mar 19 – Mar 26 | Apr 23 – Apr 30 | Jun 12 – Jul 2 | — |
| Summer squash / zucchini | Tender | — | Apr 23 – Apr 30 | Jun 7 – Jun 22 | — |
| Bush bean | Tender | — | Apr 23 – Apr 30 | Jun 12 – Jun 22 | Aug 29 – Sep 8 |
| Sweet corn | Tender | — | Apr 16 – Apr 30 | Jun 15 – Jul 15 | — |
| Basil | Very tender | Mar 5 – Mar 19 | Apr 23 – Apr 30 | May 23 – Jun 7 | — |
| Lettuce | Half-hardy | Mar 5 – Mar 19 | Mar 19 – Apr 2 | May 3 – May 18 | Aug 15 – Aug 30 |
| Pea | Hardy | — | Mar 5 – Mar 19 | Apr 29 – May 14 | Aug 5 – Aug 20 |
| Spinach | Hardy | — | Mar 5 – Mar 19 | Apr 14 – Apr 24 | Aug 25 – Sep 4 |
| Carrot | Half-hardy | — | Mar 26 – Apr 2 | May 25 – Jun 14 | Jul 26 – Aug 15 |
| Broccoli | Half-hardy | Feb 19 – Mar 5 | Mar 19 – Apr 2 | May 13 – Jun 2 | Jul 31 – Aug 20 |
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 USW00094846. 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 | Apr 29 | May 13 | Oct 18 | Oct 30 | 170 |
| 32°F (freeze) | Apr 16 | May 1 | Oct 28 | Nov 11 | 193 |
| 28°F | Apr 5 | Apr 19 | Nov 7 | Nov 22 | 217 |
| 24°F | Mar 24 | Apr 8 | Nov 17 | Dec 2 | 238 |
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) | 3,331 | standard warm-season base (tomato, corn, beans) |
| Base 40°F (cool-season) | 5,548 | cool-season crops (brassicas, greens) |
Hardiness zone 5b
Roselle 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 Roselle?
- Roselle, 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 Roselle?
- The average (median) last spring frost at 32°F is around April 16, 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 1, so wait until then before setting out frost-tender plants if you want to be safe.
- When is the first fall frost in Roselle?
- The average first fall frost at 32°F is around October 28. That leaves a growing season of about 193 days between the average last spring and first fall frosts.
- When should I start tomatoes in Roselle?
- Start tomato seeds indoors about Feb 19 – Mar 5 and transplant them outside about Apr 23 – Apr 30, once the danger of frost has passed. Estimated first harvest is around Jun 22 – Jul 12.
- How long is the growing season in Roselle?
- About 193 days at the 32°F threshold (NOAA 1991–2020, median) — the span between the average last spring frost (~April 16) and the average first fall frost (~October 28). 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 USW00094846 (Chicago Ohare Intl Ap, 10.4 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.