Frost dates for Harrisburg Hcn, Illinois
Half of years have their last spring frost by April 7 — but 1 year in 10 still frosts after April 25.
Every other site gives you one date. A frost date is not a date: it is a percentile from 30 years of records at a nearby weather station, and planting to the median means losing the crop in half of years. Both numbers are below, so you can choose the risk yourself.
The odds
Last spring frost
- Frost this late in 1 year in 10
- April 25
- 1 year in 5
- April 18
- 3 years in 10
- April 14
- 2 years in 5
- April 10
- Half of years (the median)
- April 7
First fall freeze
- Freeze this early in 1 year in 10
- October 10
- 1 year in 5
- October 16
- 3 years in 10
- October 21
- 2 years in 5
- October 23
- Half of years (the median)
- October 26
- Growing season
- about 202 days
- Hardiness zones nearby
- 6b, 7a
Where these numbers come from
NOAA NCEI 1991–2020 Climate Normals, station Harrisburg Hcn (USC00113879), at 37.74, -88.52. These are that station's own records, unshifted. The further your garden is from it, the less exactly they describe your ground — the planner resolves the nearest station to your own ZIP and lowers its confidence with distance, rather than presenting one number as if it were measured in your yard.
Cold air also pools in low ground on the clear, still nights when frost happens, so a hollow can freeze while a slope a hundred metres away does not. No table can know that about your garden. Your own logged frosts eventually can.
ZIP codes nearest this station
62817, 62829, 62856, 62859, 62867, 62869, 62871, 62890, 62917, 62922, 62928, 62930, 62931, 62934, 62935, 62946, 62947, 62954, 62965, 62967, 62972, 62974, 62977, 62979, 62984, 62985, 62987.
What can I plant here, and when? →
Nearby stations
The nearest stations, and how their last-frost dates compare — the frost gradient across your area, which no single station shows.
- Carbondale Southern Il Ap, IL — last frost by April 9
- Grand Chain Dam, IL — last frost by April 3
- Belleville Siu Rsch, IL — last frost by April 12
- Rochester Ferry, KY — last frost by April 15
- Ramsey, IL — last frost by April 15
- Festus, MO — last frost by April 9
Other stations in Illinois.
- Carlinville Hcn, IL — last frost by April 14
- Decatur Ap, IL — last frost by April 16
- Springfield #2, IL — last frost by April 15
- Danville Hcn, IL — last frost by April 21
- Rantoul, IL — last frost by April 21
- Congerville 2Nw, IL — last frost by April 21
- Peoria Gtr Peoria Ap, IL — last frost by April 16
- Hennepin, IL — last frost by April 18