Warm afternoons and cool nights ahead

The only clouds in the whole state of TN right now are right here across the Plateau. Hopefully, these will burn off soon and give us the sunny day we’re expecting to have. Highs this afternoon should reach into the mid 70s, with lows tonight dipping into the low 50s. Tomorrow we’ll see much of the same but another dry cold front will move in Friday night and that will keep highs only in the upper 60s to 70 on Saturday. We’ll be in the mid 40s for both Saturday and Sunday nights. Sunday will be the first day of October.

I wrote a piece for the Livingston Enterprise newspaper on frost and I’m including it below. I hope you enjoy it! And no worries, we’re safe from frost for at least the next 10 days.

Frost

It’s that time of year when we start looking for our first frost. Some dread seeing those little ice crystals on the ground, while others see frost as a welcome relief for their ragweed allergies.

You may have wondered how it can frost if the temperature is above freezing. After all, ice cannot form unless the temperature is at or below 32 degrees. So, how can we have frost when the forecast calls for lows in the middle 30s?

An important thing to know is that the standard height for a thermometer is about four feet above the ground. On clear nights any heat that built up during the day can easily escape into the atmosphere. If it is a cloudy night the clouds will act as a blanket and radiate the heat back toward the earth, keeping us warmer than we would otherwise be.

The ground loses its heat very quickly and that colder ground cools the air in contact with it. This causes the air nearest to the ground to be colder than the air a few feet above the ground. Wind will mix the air up and prevent frost, so you must have calm winds.

So, while your thermometer may say 35 degrees, the temperature at the ground may be a few degrees colder at 32 degrees. Our average first frost comes around the middle of October, though we have had frost as early as September 21 (1956 and 1983).

As James Whitcomb Riley once wrote,

“O, it’s then’s the times a feller is a-feelin’ at his best, With the risin’ sun to greet him from a night of peaceful rest,

As he leaves the house, bareheaded, and goes out to feed the stock,

When the frost is on the punkin and the fodder’s in the shock.”

 

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