Coldest time of year tilts later in the East, NOAA analysis finds | The Weather Channel – Articles from The Weather Channel

  • Mid-January to late January is the coldest time of year in the Midwest and Northeast.
  • But in recent years, that typical date has moved a few days later east of the Rockies.
  • This is due to warming in winter, the fastest warming season in the United States.

It’s now the coldest time of year for many in the Northeast and Midwest, but that date is shifted a bit later in the winter due to climate change, according to a just-released analysis. .

NOAA’s National Centers for Environmental Information (NCEI) has produced updated maps illustrating when the coldest day of the year, on average, occurs in the United States, based on the latest version of normals. over 30 years ending in 2020.

From the Northern Plains to the Midwest, Southeast, and Northeast, the last two weeks of January are typically the coldest time of the year. Only parts of northern Michigan are typically coldest after February 1.

Temperatures for the time of year are typically the coldest, based on the latest 30-year average temperatures from 1991 to 2020.


These maps are not forecasts, but rather show the average time to arrival of the coldest air of the season. In any given year, the actual coldest day for your area may occur before or after the time shown on the maps.

They are derived from the NCEI US Climate Normals, a dataset consisting of the latest 30-year average of weather data, including daily high and low temperatures, for various cities in the United States.

But the NOAA analysis found something interesting comparing the latest release of data from 1991 to 2020 with the previous 30-year period (1981 to 2010).

They found a “small but noticeable change” in the average coldest day 3-6 days later or more in many locations east of the Rockies compared to the 1981-2010 period.

Data from 1991 to 2020 showed more warming in early winter than later east of the Rockies, according to NOAA.

This is consistent with a previous Climate Central study that found winter to be the fastest warming season east of the Rockies and in Alaska.

The fastest warming season since 1970, by state. Winter is the fastest warming season in blue shaded states.

(Map and analysis: Climate Central; Data: NOAA)

NOAA found that the average coldest day also moved later in the Northwestern United States, but the rest of the West failed to show such a pattern.

From the Front Range of the Rocky Mountains westward, this coldest time of year is usually much earlier in December or early January.

The reason for this east-to-west discrepancy is the frequent drop of chilled frigid Arctic air over Alaska and Canada in the Midwest and Northeast in January. West of the Rockies, these mid-winter arctic loons are less common. Instead, Pacific storms can usher less cold air into the West, even in the depths of winter.

In Alaska, the coldest time of year is usually January. In Hawaii, much of the island chain experiences its coldest day, relatively speaking, in February or early March.

For most places in North America, the day of the year when the coldest temperature occurs is typically a week or more after the coldest mid-low temperatureaccording to Brian Brettschneider, a climatologist at the University of Alaska Fairbanks.

The coldest temperatures of the year usually occur when extremely cold arctic air in Canada is pulled south towards the United States. These arctic outbreaks usually occur around the average coldest time of the year.

The coldest daily average low temperature of the year, based on average data from 1991 to 2020.

(Data: NOAA/NWS)

For example, the late January 2019 cold outbreak was by far the coldest air of the season in much of the Midwest, parts of the Northeast Urban Corridor, and the Deep South.

But it’s not always the case.

Another outbreak of freezing cold in early March 2019 was the coldest of the season in Great Falls, Montana (minus 32 degrees); Dallas (21 degrees); and Wichita, Kansas (2 degrees).

When all-time records were set

A number of locations set their all-time lows in December, January or February.

All-time record highs for a number of locations across the United States

(Data: NOAA/NWS)

Boston, New York’s Central Park, and Philadelphia all set their records during a cold outbreak on February 9, 1934. Washington, DC, set its record on February 11, 1899.

Many Midwestern cities set their all-time records in January, including Chicago (January 20, 1985), Cleveland (January 19, 1994), and Minneapolis-St. Paul (January 21, 1888).

In the South, the January 1985 cold outbreak set all-time records that still stand in Charlotte and Raleigh, North Carolina; Charleston, South Carolina; and Nashville, Tennessee. However, the historic February 1899 cold outbreak, arguably the largest in modern history, is still Atlanta’s all-time record holder; Dallas; Little Rock, Arkansas; and Tallahassee, Florida, among other cities.

The all-time cold record in the West ranged from December 11, 1932 in downtown San Francisco to February 15, 1936 in Great Falls, Montana. Anchorage (minus 34 degrees) and Fairbanks (minus 66 degrees) each set their all-time cold records in early to mid-January.

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