WeatherUnderground:

Not a Historic Cold Wave

As notable as this week’s cold wave was–bringing the coldest air seen since 1996 or 1994 over much of the nation–the event failed to set any monthly or all-time record low minimum temperature records at airports and cooperative observing stations monitored by NOAA’s National Climatic Data Center. As wunderground’s weather historian Christopher C. Burt summed it up for me, “The only significant thing about the cold wave is how long it has been since a cold wave of this force has hit for some portions of the country–18 years, to be specific. Prior to 1996, cold waves of this intensity occurred pretty much every 5-10 years. In the 19th century, they occurred every year or two (since 1835). Something that, unlike the cold wave, is a truly unprecedented is the dry spell in California and Oregon, which is causing unprecedented winter wildfires in Northern California.“

Part of the reason that this week’s cold wave did not set any all-time or monthly cold records is that it is becoming increasingly difficult to do so in a warming climate. As Andrew Freedman of Climate Central wrote in a blog post yesterday, “While the cold temperatures have been unusual and even deadly, climate data shows that intense cold such as this event is now occurring far less frequently in the continental U.S. than it used to. This is largely related to winter warming trends due to man-made global warming and natural climate variability.” For example, in Detroit during the 1970s, there were an average of 7.9 nights with temperatures below zero. But this decade, that number has been closer to two nights.