- The first frost occurs on a different date, on average, in each region of the United States.
- Different weather conditions each year can cause the first frost to occur earlier or later than average.
- Mountainous regions generally reach 32 degrees before areas less influenced by the relief.
The first frost of the season may be here before you know it.
In fact, parts of the Northern Plains and the Rocky Mountains have already experienced their first frost, as well as snow accumulation.
But when does the first frost usually occur? Below, we’ll break it down by approximate average date. This is calculated by taking an average of the first frost dates over a 30 year period from 1991 to 2020.
Keep in mind, however, that these are average dates. Different weather conditions each year can cause the first frost to occur earlier or later than indicated for a given region.
The first mean freeze occurs around September 15 for much of the Rockies and parts of the Intermountain West, as well as parts of the northern plains closer to the Canadian border.
The highest peaks of Maine’s Mahoosuc Range, New Hampshire’s White Mountains, Vermont’s Green Mountains, and New York’s Adirondacks also drop to freezing around September 15.
At the end of the month, much of the Great Basin, the High Plains, the Northern Plains and the northern Great Lakes experienced their first freeze.
Most of the Adirondacks and Catskills in New York experience temperatures of 32 degrees around September 30.
The majority of New England also gets its first frost at the end of September on average. The exception is areas closer to the coast, where this only happens a few weeks later.
Parts of northern Arizona and New Mexico experience first frost around October 1 on higher elevations, while lower elevations could take a few more weeks.
Parts of the southwest throughout much of the Central Plains and Ohio Valley as well as the northeast typically hit 32 degrees around mid-October.
The Great Smoky Mountains in eastern Tennessee and western North Carolina also experience their first freeze around mid-October, as well as the Shenandoah Valley in western Virginia and much of Virginia. -Western.
(AFTER: October Temperature Outlook)
November or later
Parts of the Southwest, Southern Plains, Mid-Mississippi and Ohio Valleys, and Mid-Atlantic don’t see their first frost, on average, until Nov. 1.
This includes New York, Philadelphia, Baltimore, and Washington, DC, due to the urban heat island effect, keeping cities warmer than their suburbs at night.
Parts of California, the Southwest, the Southern Plains, the lower Mississippi Valley, and the Southeast don’t see their first frost until around November 15, on average.
In the southernmost parts of these regions, such as southeast Texas through southern Alabama and the coastal Carolinas, southern Georgia and all of Florida, it can be December or January before it starts reaches 32 degrees, if at all.
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