Chicago's winters are warming

Chicago has a well deserved reputation for some brutal winters.   The Arctic outbreak during a "polar vortex" event at the end of January 2019 comes to mind.  O'Hare dropped to -23° on January 30th that year.   While we are vulnerable to big snows and bitter cold, overall our winters have been getting warmer through the last 50 years.

Chicago's winters have warmed just over 3°since 1970 according to a study by Climate Central.  Nearly 98% of the 246 locations they studied had an increase in their average winter temperatures over the past 50 years.  84% of those locations have warmed by 2° or more.  Since 1970 winter is the fastest-warming season for most of the country.

Chicago has seen an increase of 10 more "warm winter days" since 1970.  Nearly 74% of the locations they looked at in their study had at least 7 more days above the 1991-2020 winter normal temperatures since 1970.  Climate Central defines "warm winter days" as days where the average temperature was above the 1991-2020 NOAA/NCEI climate normal. 

The greatest amount of winter warming has been occurring in the Midwest and Northeast regions.  Milwaukee has warmed 6° while Green Bay has warmed 5.8°.  They are two of the top five locations that have seen the most warming.

Climate Central points out that for some of us a warmer winter sounds ok.  However, warmer winters come with their share of problems that include the follow:

  • Migrating pests: Disease-carrying insects such as mosquitoes and ticks can migrate to regions that were previously too cold to inhabit.
  • Less snow and ice for winter sports: The multi-billion dollar winter recreation industry, which includes skiing, ice fishing, and snowmobiling, could take an economic hit because of rising temperatures and less snow/ice accumulation.
  • Water supply risk: Warmer winters can lead to declining snowpacks in the West—a necessary source of meltwater that helps refill reservoir levels and irrigate crops in the spring.
  • Lower fruit yields: Cherry, apple, and peach trees require a minimum number of winter chill hours before they can develop fruit in the subsequent spring and summer months. With the warming winter trends, this chill period is decreasing and could eventually limit fruit development.

The trend may be towards warmer winters but that doesn't mean we will escape future big snowstorms or invasions of the polar vortex.  Climate Central says "the likelihood of extreme cold conditions in a warming world is decreasing but it is not zero."  So don't put away the shovels or parkas just yet.