Frost dates · USDA zone 6a
Frost dates for Mount Prospect, IL
Mount Prospect, IL sees its last 32 °F night of spring around April 19 and its first of fall around October 26 — a 190-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 4 | Nov 9 |
| Median — 1 year in 2 | Apr 19 | Oct 26 |
| 1 year in 10 | May 3 | Oct 13 |
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: 190 days median, at least 170 in 9 years of 10, at least 207 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 5 and first of Nov 7.
Mount Prospect planting calendar, 2027
Every row runs from the median last frost (Apr 19) and median first frost (Oct 26) 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 25 | Mar 22 | Jul 10 | 110 from transplant |
| Mustard greensGarnet Giant (Brassica juncea) | Direct sow | Apr 19 | May 19 | 30 from sow |
| CilantroSlow Bolt (Coriandrum sativum) | Apr 5 | Apr 5 | May 20 | 45 from sow |
| Genovese BasilGenovese | Mar 22 | May 3 | Jul 2 | 60 from transplant |
| CayenneLong Slim Cayenne (Capsicum annuum) | Feb 22 | Apr 26 | Jul 10 | 75 from transplant |
| HabaneroOrange Habanero (Capsicum chinense) | Feb 8 | May 3 | Aug 6 | 95 from transplant |
| JalapeñoEarly Jalapeño (Capsicum annuum) | Feb 22 | Apr 26 | Jul 10 | 75 from transplant |
| Marconi Red PepperMarconi Red (Capsicum annuum) | Feb 22 | Apr 26 | Jul 15 | 80 from transplant |
| SerranoSerrano Tampiqueño (Capsicum annuum) | Feb 22 | Apr 26 | Jul 15 | 80 from transplant |
| Nantes CarrotScarlet Nantes | Apr 5 | Apr 5 | Jun 14 | 70 from sow |
| TomatilloToma Verde | Mar 8 | Apr 26 | Jul 5 | 70 from transplant |
| Roma TomatoRoma VF (determinate paste) | Mar 8 | Apr 26 | Jul 10 | 75 from transplant |
| San Marzano TomatoSan Marzano (indeterminate paste) | Mar 8 | Apr 26 | Jul 15 | 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 Mount Prospect grow?
Each sauce, scheduled for a Mount Prospect container garden: when the first seeds go in and when enough fruit has ripened for one batch.
Mount Prospect frost questions
When is the last frost in Mount Prospect, IL?
The median last 32 °F freeze at CHICAGO PALWAUKEE AP, IL is April 19: half of years see a later one. One year in ten, a freeze still comes after May 3; nine years in ten, it comes after April 4. Source: NOAA NCEI 1991–2020 U.S. Climate Normals.
When is the first frost in Mount Prospect, IL?
The median first 32 °F freeze of fall is October 26. One year in ten it arrives before October 13; nine years in ten, before November 9.
How long is the growing season in Mount Prospect, IL?
190 days between the last spring and first fall 32 °F freeze in a median year. Nine years in ten the season runs at least 170 days; one year in ten, at least 207 days.
What growing zone is Mount Prospect, IL?
USDA hardiness zone 6a, per the 2023 USDA Plant Hardiness Zone Map for ZIP 60056. 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 Mount Prospect, IL?
Start Roma VF (determinate paste) seeds indoors around Mar 8 and transplant around Apr 26, 1 week after the median last frost. To cut the freeze risk to one year in ten, wait for May 3. First ripe fruit lands around Jul 10.
When should I plant peppers in Mount Prospect, IL?
Sow jalapeño indoors on a heat mat around Feb 22; transplant no earlier than Apr 26, and wait past it until nights hold above 50 °F — that can run weeks later. First green pods around Jul 10.
Nearby in Illinois
- Des Plaineslast frost Apr 16
- Arlington Heightslast frost Apr 19
- Glenviewlast frost Apr 19
- Palatinelast frost Apr 25
- Buffalo Grovelast frost Apr 19
- Schaumburglast frost Apr 30
All Illinois frost dates → · How frost-date math drives a sowing calendar →