It seems like in the blink of an eye we’ve gone from sunny summer days to fresh fall festivities. In fact, Ohio’s daytime highs have fallen 20 degrees from late September to early October!

What You Need To Know

  • The first frost/freeze will occur on different dates each year, but it’s important to know the average date

  • Different weather conditions each year can make the first freeze occur earlier or later than average

  • This October starts below average, so frosty mornings are likely in Ohio

Let’s break down the difference between frost and freeze first.

Frost

Frost is a layer of ice crystals that form when water vapor on plant matter condenses and freezes without first becoming dew.

The ideal overnight low for frost is between 33 to 39 degrees with fairly clear skies and little to no wind. The ground releases heat overnight and fewer clouds means more heat escapes back to space. This is called radiational cooling.

Little to no wind at night prevents the air from getting stirred up. The ground temperature can be up to 10 degrees cooler than where the temperature observation is takek, typically four to five feet above the surface.

Another major factor in the development of frost and freeze is location! Valleys are ideal for development of frost and freeze because as the cold air is heavier than warmer air and settles into valleys and low spots. This also creates a shelter from stronger winds and can enhance the potential for frost/freeze by morning.

Frosts tend to occur late at night or in the early hours of the morning. Tender plants probably suffer some damage while the hardier plants survive.

Freeze

Toward the end of the growing season, freeze becomes inevitable as temperatures drop below freezing. A process called advection cooling can cause freezes to occur. Advection is when there is a transferring of heat or moisture by movement of an air mass. 

Unlike frost events, freezes can be either short or long term. 

A hard freeze is a period of at least four consecutive hours of air temperatures at our below 28 degrees. This usually will create widespread damage on plants.

Know the alerts

Here are the definitions of the National Weather Service's frost and freeze alerts. 

Frost Advisory: Issued when minimum temperatures are expected to be between 33 to 36 degrees. Skies are generally clear with calmer winds.

Freeze Watch: Issued when the minimum temperatures are expected to be 32 degrees or colder within the next 24 to 36 hours.

Freeze Warning: Issued when minimum temperatures are imminently expected to be 32 degrees or colder.

Hard Freeze Warning: Issued when minimum temperatures are expected to be 28 degrees or colder.

Know the dates

Keep in mind these are averages, and every year it varies.

Below are the average first freeze dates for various cities in Ohio:

Akron-Canton: October 19

Bellefontaine: October 14

Chillicothe: October 17

Cincinnati: October 24

Circleville: October 19

Cleveland: October 28

Columbus: October 27

Dayton: October 22

Delaware: October 14

Greenville: October 12

Kenton: October 20

Mansfield: October 14

Marysville: October 22

Portsmouth: October 23

Springfield: October 13

Toledo: October 17

Wilmington: October 16

Xenia: October 20

Youngstown: October 14

Zanesville: October 14