Frigid air has been in short supply this winter in much of North America, leading to generally mild conditions for much of the Lower 48. The more limited cold air has also reduced the amount of snow in some areas.

However, it is important to keep in mind that the term "mild" is relative, especially in winter, and refers to warmer than average temperatures.

Most locations in the U.S. have experienced a mild or moderate winter, according to the Accumulated Winter Season Severity Index (AWSSI) from the Midwestern Regional Climate Center. This is shown in the map above by the red and orange dots which dominate the graphic.

This index categorizes locations by taking into account the intensity and persistence of cold weather, the total amount of snowfall and the amount and persistence of snow on the ground.

Only a handful of locations are in the "severe" category and we're just over the halfway mark in meteorological winter, which is from Dec. 1 through Feb. 28. No locations in the U.S. have had an extreme winter as of Jan. 18.

The persistent above-average temperatures mean several areas have experienced their warmest winter on record through Jan. 17, according to the Southeast Regional Climate Center.

This includes some typically cold locations, like Glasgow, Montana, where the average temperature so far this season has been 29.2 degrees – more than 14 degrees warmer than average. It has also been the third-driest winter to date there.

Another example is International Falls, Minnesota, sometimes referred to as the "Icebox of the Nation." Their winter has been the second-warmest on record so far, and the average temperature this season has been 19.4 degrees, which is still very cold by most standards.

This winter is also the warmest on record so far in Grand Forks, North Dakota, where there is a snowfall deficit of 13.7 inches. Farther east, Sault Ste. Marie has measured about 33 fewer inches of snow than average this season and is tied for its warmest winter.

It's not just the Northern Plains and upper Midwest that have seen unusually mild temperatures this winter.

Caribou, Maine, and Seattle, Washington, are also both experiencing their warmest winter on record to date. Temperatures in Caribou have been almost 10 degrees warmer than average for the season. Seattle's mean temperature is about 4 degrees above average; It has also been the fourth-wettest winter on record there.

The map below shows that if you are looking for a colder-than-average winter, it's been in the Southeast. Chillier-than-usual conditions have been the story in parts of the southern tier, although it hasn't been record-breaking cold.

Changes may be ahead as we head into the second half of winter.

The upper-level pattern is expected to shift a bit in late January and could allow for a colder pattern to emerge in the Lower 48. This could result in chillier temperatures and more snow across the northern tier, changing the warm theme that has prevailed so far this winter.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.