Frost dates · USDA zone 6a
Frost dates for Decatur, IL
Decatur, IL sees its last 32 °F night of spring around April 14 and its first of fall around October 24 — a 192-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 1 | Nov 5 |
| Median — 1 year in 2 | Apr 14 | Oct 24 |
| 1 year in 10 | May 1 | Oct 11 |
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: 192 days median, at least 171 in 9 years of 10, at least 211 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 3 and first of Nov 3.
Decatur planting calendar, 2027
Every row runs from the median last frost (Apr 14) and median first frost (Oct 24) 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 20 | Mar 17 | Jul 5 | 110 from transplant |
| Mustard greensGarnet Giant (Brassica juncea) | Direct sow | Apr 14 | May 14 | 30 from sow |
| CilantroSlow Bolt (Coriandrum sativum) | Mar 31 | Mar 31 | May 15 | 45 from sow |
| Genovese BasilGenovese | Mar 17 | Apr 28 | Jun 27 | 60 from transplant |
| CayenneLong Slim Cayenne (Capsicum annuum) | Feb 17 | Apr 21 | Jul 5 | 75 from transplant |
| HabaneroOrange Habanero (Capsicum chinense) | Feb 3 | Apr 28 | Aug 1 | 95 from transplant |
| JalapeñoEarly Jalapeño (Capsicum annuum) | Feb 17 | Apr 21 | Jul 5 | 75 from transplant |
| Marconi Red PepperMarconi Red (Capsicum annuum) | Feb 17 | Apr 21 | Jul 10 | 80 from transplant |
| SerranoSerrano Tampiqueño (Capsicum annuum) | Feb 17 | Apr 21 | Jul 10 | 80 from transplant |
| Nantes CarrotScarlet Nantes | Mar 31 | Mar 31 | Jun 9 | 70 from sow |
| TomatilloToma Verde | Mar 3 | Apr 21 | Jun 30 | 70 from transplant |
| Roma TomatoRoma VF (determinate paste) | Mar 3 | Apr 21 | Jul 5 | 75 from transplant |
| San Marzano TomatoSan Marzano (indeterminate paste) | Mar 3 | Apr 21 | Jul 10 | 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 Decatur grow?
Each sauce, scheduled for a Decatur container garden: when the first seeds go in and when enough fruit has ripened for one batch.
Decatur frost questions
When is the last frost in Decatur, IL?
The median last 32 °F freeze at DECATUR WTP, IL is April 14: half of years see a later one. One year in ten, a freeze still comes after May 1; nine years in ten, it comes after April 1. Source: NOAA NCEI 1991–2020 U.S. Climate Normals.
When is the first frost in Decatur, IL?
The median first 32 °F freeze of fall is October 24. One year in ten it arrives before October 11; nine years in ten, before November 5.
How long is the growing season in Decatur, IL?
192 days between the last spring and first fall 32 °F freeze in a median year. Nine years in ten the season runs at least 171 days; one year in ten, at least 211 days.
What growing zone is Decatur, IL?
USDA hardiness zone 6a, per the 2023 USDA Plant Hardiness Zone Map for ZIP 62523. 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 Decatur, IL?
Start Roma VF (determinate paste) seeds indoors around Mar 3 and transplant around Apr 21, 1 week after the median last frost. To cut the freeze risk to one year in ten, wait for May 1. First ripe fruit lands around Jul 5.
When should I plant peppers in Decatur, IL?
Sow jalapeño indoors on a heat mat around Feb 17; transplant no earlier than Apr 21, and wait past it until nights hold above 50 °F — that can run weeks later. First green pods around Jul 5.
Nearby in Illinois
- Springfieldlast frost Apr 15
- Champaignlast frost Apr 15
- Bloomingtonlast frost Apr 21
- Normallast frost Apr 25
- Peorialast frost Apr 16
- Jolietlast frost Apr 19
All Illinois frost dates → · How frost-date math drives a sowing calendar →