First Freeze Delays Across the U.S. Linked to Climate Change

You may be waiting for the first signs of winter for quite some time. Climate change is pushing back the arrival of the coldest season of the year, impacting the weather patterns in a number of noticeable ways. This is what you need to know.

Dates of First Freeze Delayed as a Result of Climate Change

Climatologists have known for some time that the seasons are not changing as they normally do in recent decades. As the planet gradually warms, the autumn season is also heating up and delaying the average date of the first freeze for much of the U.S. This delay in the season's first freeze has widespread implications for allergens, agricultural interests, and more.

According to the nonprofit research group Climate Central, the first freeze in the U.S. has moved back an average of 11 days in 85% of 200 metro areas since 1970. The most significant changes have been observed in the Midwest and the Northeast.

The date of the first freeze is driven by a variety of factors. These include general elevation, urban density, or proximity to an ocean or other big body of water. Most of these elements begin to work together to produce the first freeze of the year as early as September for the top terrains of the northern and central Rockies, as well as the Dakotas, the northern edge of the Great Lakes, and the highest elevations of New England.

Data from the National Oceanic and Atmospheric Administration (NOAA) also details that the first freeze of the season typically begins in October for the Midwest, the Northeast, and the interior West. The southern U.S. generally has to wait until November to see its first freeze.

However, freeze dates have been rolled back over the last few decades. The biggest change has been cited in the northern fringe of the country. For example, the data indicates that this major weather event has been pushed back at least two weeks when compared to 1970 across five dozen cities. Most of these urban areas are located in the Northeast and the Upper Midwest. This includes the cities of Philadelphia, Minneapolis, and Detroit.

However, some cities in the Pacific Northwest and the interior West have also experienced this delay. For example, Reno, Nevada, has seen the largest shift with a first freeze date now landing 41 days later when compared to 1970.