When will Central KY see its first fall frost? It may be sooner than you think
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- National Weather Service forecasts a cold front that could bring frost next week.
- Frost forms under clear skies, calm winds and low 30s overnight lows in valleys.
- Historical NWS data show frost chances climb from 40% mid‑October to 90% by Oct. 30.
It may just be starting to feel like fall with temperature highs in Lexington hovering in the 70s this week and climbing toward 80 degrees Saturday, but a wave of autumn storms is expected to soon change that.
Gardeners, farmers and even homeowners hoping to slow down on mowing are likely anticipating the first frost of the season, and while several factors need to line up to make that happen, there is a chance of it next week.
If you’re looking ahead to a winter filled with fluffy white snow, the best chance for it is in January, if at all, according to this year’s outlooks. The weak La Niña conditions in effect aren’t likely to influence Kentucky’s chance for a snowier winter.
Here’s what we know about when to expect the first frost of the season in Central Kentucky this year.
When will Kentucky see its first frost this fall?
Local topography plays a big role in frost formation. As explained by Kyle Wilkins, a meteorologist with the National Weather Service in Louisville, it usually needs to get pretty cool before urban areas, like Lexington, see their first autumn frost.
“Frost usually happens when you have clear skies that allow for radiative cooling, calm winds, and low enough temperatures,” Wilkins wrote the Herald-Leader in an emailed response. “Generally you see this happen first in valleys where cold air sinks or grassy areas surrounded by trees to block the wind. We will need to see lows in the 30s before you see frost in the cities.”
According to the agency, a frost forms with an air temperature range between 33 and 36 degrees Fahrenheit, along with light winds. It can inflict at least minor damage to plants, but tender plants are especially vulnerable.
Freezes and hard freezes occur when temperatures drop below 32 degrees. They inflict more significant damage to exposed plants. Hard freezes will kill most seasonal plant varieties, as well as possibly damage exposed outdoor plumbing and undrained sprinkler systems.
The latest NWS forecast shows temperature highs around or above 70 degrees for Lexington this week, including a high of 80 degrees Saturday, Oct. 18. Nightly lows throughout the week will be cool, but nowhere near the 30s.
That pattern could change Saturday, however, with the arrival of showers and thunderstorms overnight Saturday and into Sunday, according to WKYT Chief Meteorologist Chris Bailey. The weekend cold front will bring below-normal temperatures to our area, along with more autumn storms.
“This pattern may very well bring frost with it at some point next week,” Bailey wrote in an Oct. 14 forecast.
Along with keeping your eye on warnings, watches and advisories from the weather service, there’s a set of conditions to watch for when trying to anticipate frost.
“As far as overall set-ups, having an upper ridge with surface high over us would help with frost formation because it would clear skies and keep winds light, allowing for cool nights,” Wilkins wrote. “A lot of times behind cold fronts you have these conditions.”
Historical averages from the NWS offer another frost clue
Looking at historical averages compiled by the NWS, frosts and freezes in the Lexington area become increasingly likely by the tail-end of October and early November.
NWS data between 1991 and 2020 show there’s a 40% chance temperatures will fall to 36 degrees Fahrenheit by Oct. 16. By Oct. 19 and 21, the chance is 50 and 60%, respectively. But by Oct. 30, it’s almost a guarantee with a 90% chance.
When it comes to records, the weather service reports the following for the Lexington area:
- Earliest fall frost (36 degrees): Sept. 23, 1896; Sept. 23, 1974; Sept. 23, 2012
- Earliest fall freeze (32 degrees): Sept. 30, 1899
- Earliest fall hard freeze (28 degrees): Oct. 3, 1974
- Latest first fall frost (36 degrees): Nov. 9, 1922
- Latest first fall freeze (32 degrees): Nov. 27, 1902
- Latest first fall hard freeze (28 degrees): Dec. 4, 1899
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