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Weekend predictions of a 28 degree killing frost

Posted: Wed, Oct 9, 2019 10:03 AM

A portion of NW Iowa will very likely experience a killing frost this weekend with temperatures of 28 degrees or less. This can affect corn, soybeans and warm-season annual forages (i.e. sorghums and millets).

What will happen in NE Iowa? The National Weather Service (NWS) predicts nothing lower than 32 degrees, but AccuWeather is less optimistic. If we make it through this weekend in good condition, the next killing frost threat is not predicted until around October 27th.
Friday thru Sunday night lows according to NWS/AccuWeather:
Lime Springs - 32 degrees/27 degrees
St Ansgar- 32 degrees/29 degrees
Cresco - 32 degrees/28 degrees
Decorah - 33 degrees/29 degrees
Waukon - 34 degrees/29 degrees

How will the temperatures affect the area's corn and soybeans? A partial frost that kills some leaf area has the same effect on yield reductions as insect feeding, foliar fungicide lesions, and hail damage. Corn that was defoliated 60% (moderate frost) at the dent stage would have about a 10% yield loss.