Frost dates for Hennepin, Illinois
Half of years have their last spring frost by April 18 — but 1 year in 10 still frosts after May 3.
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
- May 3
- 1 year in 5
- April 29
- 3 years in 10
- April 23
- 2 years in 5
- April 21
- Half of years (the median)
- April 18
First fall freeze
- Freeze this early in 1 year in 10
- October 7
- 1 year in 5
- October 14
- 3 years in 10
- October 17
- 2 years in 5
- October 19
- Half of years (the median)
- October 22
- Growing season
- about 188 days
- Hardiness zone nearby
- 5b
Where these numbers come from
NOAA NCEI 1991–2020 Climate Normals, station Hennepin (USC00114012), at 41.25, -89.34. 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
61301, 61312, 61315, 61316, 61317, 61320, 61322, 61323, 61326, 61327, 61328, 61329, 61334, 61335, 61336, 61337, 61340, 61349, 61354, 61356, 61359, 61362, 61363, 61368, 61369, 61370, 61375, 61376, 61377, 61379, 61537, 61540, 61541, 61560, 61565.
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.
- Congerville 2Nw, IL — last frost by April 21
- Peoria Gtr Peoria Ap, IL — last frost by April 16
- Clinton #1 Hcn, IA — last frost by April 22
- Aurora Hcn, IL — last frost by April 19
- Rockford Gtr Rockford Ap, IL — last frost by April 24
- Aledo Hcn, IL — last frost by April 22
Other stations in Illinois.
- Chicago Midway Ap 3Sw, IL — last frost by April 10
- Rantoul, IL — last frost by April 21
- Mc Henry -Wg Stratton L&D, IL — last frost by May 1
- Decatur Ap, IL — last frost by April 16
- Chicago Botanic Garden, IL — last frost by April 26
- Springfield #2, IL — last frost by April 15
- Danville Hcn, IL — last frost by April 21
- Carlinville Hcn, IL — last frost by April 14