Brrr... crisp mornings have arrived in SE Wyoming. The afternoons still carry the last warmth of summer, but we all know the truth - the chill of Autumn is on the horizon. But when can we expect frost to glisten on our gardens and lawns?

When Will the First Frost Arrive in SE Wyoming?

Autumn can appear instantly here in Wyoming - one minute, we're sitting at 80 degrees, and the next, snow and sleet are knocking on our door. With September underway, it's only a matter of time before frigid temps start appearing in the Equality State.

According to the knowledgeable folks at the National Weather Service (NWS), it won't take long before we see frost shimmering on our lawns. Frost won't appear until temperatures dip below 32 degrees Fahrenheit. Weather data from the years 2000 to 2022 give a fair picture of when frost will arrive:

Laramie

Data from NWS indicates that Laramie's earliest freeze happened on 09/02/2008, and "its latest freeze on 09/22/2019." On average, Laramie sees its first freeze by 09/13/2019 annually.

Cheyenne

Cheyenne's data from the same time period indicates that the capital city typically has a longer window before the first frost arrives. The NWS reports Cheyenne "had its earliest freeze on 09/07/2020" and the latest on 10/25/2010. Typically, Cheyenne will have its first freeze around the first week of October, averaging an arrival of 10/03 annually.

Will the First Frost Kill Gardens & Grass?

Frost may look pretty when it glazes over your rose garden, but it's not very kind to vegetation. But the first frost usually won't annihilate plants and gardens. The Old Farmer's Almanac notes that there are three different freeze levels, and most plans can survive a light freeze - the category a first frost generally falls into. Here's a breakdown of how frost levels impact plants:

  • Light freeze: 29° to 32°F (-1.7° to 0°C)—tender plants are killed.
  • Moderate freeze: 25° to 28°F (-3.9° to -2.2°C)—widely destructive to most vegetation.
  • Severe freeze: 24°F (-4.4°C) and colder—heavy damage to most garden plants.

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