LOUISVILLE, Ky. — A dose of reality will take shape for central Kentucky and southern Indiana this week. The Fall season is officially here and with incoming cold air, our first frost of the season is in the works for our area.
No alerts are issued from the National Weather Service yet, but we want to give a heads up that temperatures will take a dip well into the middle to upper 30s Tuesday night into Wednesday morning.
This means that conditions may be ideal for frost (especially outside of Jefferson County) for midweek.
Thursday morning will again be a rather cool one but widespread frost seems unlikely at this time.
Metro Louisville will hover in the lower 40s for the morning low temperature but a few spots in central Kentucky and southern Indiana may pick up more areas of frost.
When do we normally pick up out first frost and freeze of Fall?
It all depends on the weather patterns with temperature and how the transition to Fall from Summer turns out, but we average our first frost and first freeze on the following dates:
Average first frost: October 30th (usually around 36°)
Average first freeze: November 7th (32° or colder)
Keep in mind that these are the average dates for Louisville. The averages can range by a few days or a few weeks in rural or other locations of central Kentucky and southern Indiana.
The following map is an accurate depiction of when surrounding spots outside of Jefferson County normally pick up the first frost:
How does frost form?
Frost normally forms between the temperatures of 33° and 38°. However, there is not a specific temperature that makes for frost formation. Frost is defined as forming when moisture in the air condenses (gas to a liquid) and freezes on contact with ground temperatures at the freezing point or colder.
The water vapor particles in the air turn into small ice crystals as they come in contact with objects already at freezing.
Examples of objects that frost easily forms on include:
- Grass
- Trees (branches in particular)
- The outside of your vehicle
- Plants or vegetation
- Playground equipment
Why is the first frost/freeze of the season important?
Depending on the type of plant or vegetation around your household, farm or garden, plants are negatively affected by cold air. As temperatures near or surpass the freezing point, they can wilt or die off. Therefore, it is important to make sure your plants and crops are protected and even brought indoors to prevent temporary or permanent damage!
It all depends on the type of plant or crop you are dealing with to know what kind of temperatures it can or cannot deal with as we head into the colder months. Just keep in mind that a hard freeze (temperatures at or below 28°) kill off or nearly kill off all plants and vegetation. The average date of a hard freeze in Louisville is Nov. 17th.
