Frost dates · USDA zone 6a
Frost dates for Romeoville, IL
Romeoville, IL sees its last 32 °F night of spring around April 20 and its first of fall around October 22 — a 184-day freeze-free season in a typical year.
Pick a sauce; the Plan Builder runs this station's dates and hands back the calendar, plant count and gear list.
Freeze odds, by date
| Odds | Last spring freeze after | First fall freeze before |
|---|---|---|
| 9 years in 10 | Apr 7 | Nov 3 |
| Median — 1 year in 2 | Apr 20 | Oct 22 |
| 1 year in 10 | May 6 | Oct 7 |
The top row is the risky edge: in 9 years of 10 a spring freeze still comes after it, so tender transplants set out then need cover. The bottom row is the cautious date — only 1 year in 10 freezes after it — and the one to plan uncovered tender transplants against. Freeze-free season: 184 days median, at least 162 in 9 years of 10, at least 202 days in 1 year of 10. NOAA ranks season length year by year, so it is not the gap between two rows above. A hard freeze (28 °F) has a median last date of Apr 8 and first of Nov 1.
Romeoville planting calendar, 2027
Every row runs from the median last frost (Apr 20) and median first frost (Oct 22) above, using each cultivar's days to maturity. Same engine as the Plan Builder.
| Crop | Start indoors | Transplant / plant | First harvest | Days |
|---|---|---|---|---|
| Hardneck GarlicSiberian (porcelain hardneck) | — | Oct 15prior fall | Jun 12 | 240 from sow |
| Spanish OnionYellow Sweet Spanish (long-day) | Jan 26 | Mar 23 | Jul 11 | 110 from transplant |
| Mustard greensGarnet Giant (Brassica juncea) | Direct sow | Apr 20 | May 20 | 30 from sow |
| CilantroSlow Bolt (Coriandrum sativum) | Apr 6 | Apr 6 | May 21 | 45 from sow |
| Genovese BasilGenovese | Mar 23 | May 4 | Jul 3 | 60 from transplant |
| CayenneLong Slim Cayenne (Capsicum annuum) | Feb 23 | Apr 27 | Jul 11 | 75 from transplant |
| HabaneroOrange Habanero (Capsicum chinense) | Feb 9 | May 4 | Aug 7 | 95 from transplant |
| JalapeñoEarly Jalapeño (Capsicum annuum) | Feb 23 | Apr 27 | Jul 11 | 75 from transplant |
| Marconi Red PepperMarconi Red (Capsicum annuum) | Feb 23 | Apr 27 | Jul 16 | 80 from transplant |
| SerranoSerrano Tampiqueño (Capsicum annuum) | Feb 23 | Apr 27 | Jul 16 | 80 from transplant |
| Nantes CarrotScarlet Nantes | Apr 6 | Apr 6 | Jun 15 | 70 from sow |
| TomatilloToma Verde | Mar 9 | Apr 27 | Jul 6 | 70 from transplant |
| Roma TomatoRoma VF (determinate paste) | Mar 9 | Apr 27 | Jul 11 | 75 from transplant |
| San Marzano TomatoSan Marzano (indeterminate paste) | Mar 9 | Apr 27 | Jul 16 | 80 from transplant |
Tight means first harvest lands within two weeks of the median first fall frost: start that crop indoors on time or cover it in fall.
What sauce can Romeoville grow?
Each sauce, scheduled for a Romeoville container garden: when the first seeds go in and when enough fruit has ripened for one batch.
Romeoville frost questions
When is the last frost in Romeoville, IL?
The median last 32 °F freeze at ROMEOVILLE WFO, IL is April 20: half of years see a later one. One year in ten, a freeze still comes after May 6; nine years in ten, it comes after April 7. Source: NOAA NCEI 1991–2020 U.S. Climate Normals.
When is the first frost in Romeoville, IL?
The median first 32 °F freeze of fall is October 22. One year in ten it arrives before October 7; nine years in ten, before November 3.
How long is the growing season in Romeoville, IL?
184 days between the last spring and first fall 32 °F freeze in a median year. Nine years in ten the season runs at least 162 days; one year in ten, at least 202 days.
What growing zone is Romeoville, IL?
USDA hardiness zone 6a, per the 2023 USDA Plant Hardiness Zone Map for ZIP 60446. A zone describes the coldest winter night, not when frost ends, so it is the wrong number for a planting calendar — the frost dates on this page are the right one.
When should I plant tomatoes in Romeoville, IL?
Start Roma VF (determinate paste) seeds indoors around Mar 9 and transplant around Apr 27, 1 week after the median last frost. To cut the freeze risk to one year in ten, wait for May 6. First ripe fruit lands around Jul 11.
When should I plant peppers in Romeoville, IL?
Sow jalapeño indoors on a heat mat around Feb 23; transplant no earlier than Apr 27, and wait past it until nights hold above 50 °F — that can run weeks later. First green pods around Jul 11.
Nearby in Illinois
- Bolingbrooklast frost Apr 20
- Plainfieldlast frost Apr 20
- Jolietlast frost Apr 19
- Napervillelast frost Apr 28
- Downers Grovelast frost Apr 28
- Orland Parklast frost Apr 20
All Illinois frost dates → · How frost-date math drives a sowing calendar →