Over at Slate.com, an article claims that extreme cold is becoming less common in certain locations:

A recent study by Climate Central showed that, despite its prevalence in recent winters, days with extreme cold are in a long-term decline in the United States, linked to ongoing global warming. For example, in the 1970s, Chicago used to see about 10 nights per year dipping below zero. Since 2000, the average is less than five.

Here are the number of "nights per year dipping below zero" for Chicago since records began in 1873 using data from the NOAA National Weather Service database.

Starting in the 1970s is cherry-picking, since this was a colder than usual decade.  There have been no significant trends in the number of days below zero since records began, nor over the past century, nor during the last 30 years.  In fact, the correlation over the last 100 years is positive, toward more days below zero, not fewer.

There is no evidence that anthropogenic climate change is leading to fewer days below zero in the Chicago area.

Moving over the source Climate Central "study" that gave rise to these claims, the site shows a graph of the purported declining number of nights below zero for Detroit since 1970.  So here is the Detroit data back to when records start in 1874.

No sign of anthropogenic climate change impacts here, either, and another classic example of cherry-picking when starting a time series analysis in the 1970s.  Same results as for Chicago: no significant trends since records began, nor over the past century, or during the last 30 years, and the correlation over the last 100 years is positive, toward more days below zero, not fewer.

Another dose of long-term climate reality cures the alarmism.