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Frost dates for Decatur Ap, Illinois

Half of years have their last spring frost by April 16 — but 1 year in 10 still frosts after April 30.

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 30
1 year in 5
April 25
3 years in 10
April 22
2 years in 5
April 20
Half of years (the median)
April 16

First fall freeze

Freeze this early in 1 year in 10
October 7
1 year in 5
October 12
3 years in 10
October 16
2 years in 5
October 20
Half of years (the median)
October 22
Growing season
about 187 days
Hardiness zone nearby
6a

Where these numbers come from

NOAA NCEI 1991–2020 Climate Normals, station Decatur Ap (USW00003887), at 39.83, -88.87. 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

61735, 61750, 61756, 61813, 61818, 61830, 61839, 61855, 61856, 61882, 61914, 61925, 61929, 61936, 61937, 62501, 62513, 62514, 62521, 62522, 62523, 62526, 62532, 62535, 62537, 62544, 62547, 62549, 62550, 62551, 62554, 62567, 62573.

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.

Other stations in Illinois.

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