First Killing Frost?

Frost (photo by It’s No Game via Flickr Creative Commons License)

4 November 2021

This morning Pittsburgh’s official temperature dipped to 28 degrees F at 5:51am at Pittsburgh International Airport(*) and 27 degrees an hour later. This is long enough and low enough(**) to be the first killing frost of the winter.

Weather Conditions for Pittsburgh International Airport, 4 Nov 2021 through 6:51am (image from NWS)

However, we still haven’t had a killing frost in some parts of Pittsburgh. Where I live in Oakland the low was only 31 and at the Allegheny County Airport in West Mifflin, 6.5 miles south of me, the temperature dropped briefly to 30, then rose to a steady 31.

Weather Conditions for Allegheny County Airport, 4 Nov 2021 through 6:53am (image from NWS)

Did we have a killing frost?

If you live in suburbs your garden died this morning. If you live in the city it may be fine except for very tender plants.

The City of Pittsburgh is usually 5 degrees warmer than the suburbs. That’s a big reason why crows come to town for the winter.

(photo of frost by It’s No Game via Flickr Creative Commons License, Pittsburgh weather data from

(*) Until the official data is published later today I assume that Pittsburgh International was the same temperature as Pittsburgh’s official weather station in Coraopolis, 2.88 miles away.

(**) 28 degrees F is generally considered the temperature of a killing frost and is certainly true for corn and soy farmers. Tender garden plants, such as impatiens, die just below freezing.

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