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Frost dates for Clinton #1 Hcn, Iowa

Half of years have their last spring frost by April 22 — but 1 year in 10 still frosts after May 8.

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 8
1 year in 5
May 2
3 years in 10
April 29
2 years in 5
April 26
Half of years (the median)
April 22

First fall freeze

Freeze this early in 1 year in 10
October 2
1 year in 5
October 7
3 years in 10
October 11
2 years in 5
October 13
Half of years (the median)
October 16
Growing season
about 175 days
Hardiness zones nearby
5a, 5b

Where these numbers come from

NOAA NCEI 1991–2020 Climate Normals, station Clinton #1 Hcn (USC00131635), at 41.79, -90.26. 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

52069, 52701, 52722, 52727, 52730, 52731, 52732, 52742, 52748, 52750, 52753, 52756, 52757, 52758, 52767, 52768, 52803, 52806, 52807, 61230, 61236, 61239, 61241, 61242, 61244, 61252, 61256, 61257, 61275, 61278, 61282.

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 Iowa.

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