Potential frost tomorrow, Wednesday mornings

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Autumn weather is in full swing across Kentuckiana, featuring cool days and crisp, cold autumn nights. Some areas are about to pick up on the first chance for some frost for this season. Although it may seem to be coming right on schedule, we are in fact running a little later than normal for temperatures this cold to arrive, especially in our rural locations.

NEXT TWO NIGHTS

Many areas will fall into the mid and upper 30s tonight outside the metro with downtown temperatures holding in the low 40s.

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A low temperature of 36 degrees or lower can generate frost if the air is moist and breezes are light. Typically, since air temperatures are not measured right at the ground, it is possible for frost to form with an air temp of 36 or less since it is slightly cooler right at the surface of the earth at night, due to long wave radiation.

"NORMAL" FIRST FROST

We generally see our first temperatures of 36 degrees or lower in Louisville around October 20th. This occurs much earlier in our rural areas. Take a look at the image below. Over the last 30 years a temperature of 36 degrees occurred as early as late September, on average, in places well away from Louisville's heat island.

"NORMAL" FIRST FREEZE

Freezing temperatures, of course, occur later than what is required for a light frost. We generally see our first temperatures of 32 degrees or lower in Louisville around November 4th. Take a look at the image below. Over the last 30 years a temperature of 32degrees occurred as early as early October, on average, in places well away from Louisville's heat island. In short, we are running behind schedule on freezing temperatures in rural locations already for this year!

2017 is still ranked as one of our area's warmest years on record, so not so surprising that we are waiting longer to end the growing season this go around!

Enjoy the sunny fall weather this week after some cold mornings.