An extreme winter weather event is unfolding across the Midwest on Wednesday through Thursday, and numerous daily and some all-time temperature records have been shattered.
The big picture: An air mass that originated in the High Arctic is currently swinging across the Great Lakes, sending some air temperatures plummeting below minus 30°F. Combined with winds of 40 mph at times, wind chills are reaching dangerous levels — below minus 50°F, and in some cases below minus 60°F — in parts of Minnesota, Wisconsin, Iowa, Illinois and Michigan.
Details: Typically, when cold outbreaks hit the Midwest, meteorologists take on a reassuring demeanor, letting their audience know that this is the type of cold they've experienced before.
That's not the case this time. Here's what the NWS forecast office in Des Moines stated on Tuesday:
- "THIS HAS THE POTENTIAL TO BE LIFE-THREATENING COLD AIR!!! This is the coldest air many of us will have ever experienced. This is not a case of 'meh, it's Iowa during winter and this cold happens.' These are record-breaking cold air temperatures, with wind chill values not seen in the 21st century in Iowa."
- On Wednesday, the NWS in Grand Forks, North Dakota, called conditions there, "very Hoth-like" with wind chills down to minus 64°F and occasional white-outs due to blowing snow.
Depending on the location, Wednesday and Thursday are proving to be the coldest days in 20-plus years.
- Minneapolis saw a low temperature of minus 28°F on Wednesday morning. The last time it was this cold was in 1996.
- Des Moines, Iowa, set a daily record low with a temperature of minus 20°F, and a wind chill far colder than that. At 8 am in Iowa, wind chills were as low as minus 58°F, which is sufficient to cause frostbite in just minutes.
- Chicago saw a wind chill of minus 52°F and a low of minus 23°F, which was the city's 5th-lowest temperature on record and the coldest reading since 1985. The low on Thursday morning may be even colder, and could make a run at the city's all-time record of minus 27°F.
- Chicago's all-time record for the coldest daytime high temperature is likely to be tied or broken, with temperatures only climbing to minus 11°F. Similar records are in jeopardy in South Bend, Indiana, Kalamazoo, Michigan and Rockford, Illinois.
- Residents of Minneapolis and Des Moines are being warned to limit their exposure to the cold to mere minutes, given the possibility of frostbite.
In terms of state records, both Minnesota and Illinois are going to make a run at their all-time low temperature records on Thursday, morning.
Threat level: The cold has canceled thousands of flights across the Midwest, due to the difficult working conditions on the tarmac and challenges for ground equipment to operate in such frigid temperatures. In addition, at least 5 deaths have been reported so far, though that number is expected to increase.
The climate context: This extreme weather event comes courtesy of a lobe of the polar vortex, which has swirled its way southward, out of the high Arctic, to strafe the Midwest and Northeast with a taste of the winter weather normally felt in far northern Canada.
- And we're going to be seeing more of these, although they may not be quite so severe. Even though we think of climate change as rising global temperatures, recent studies show that it could cause more frequent southward polar vortex incursions too — because as it melts Arctic sea ice, it alters the exchange of heat and moisture between the ocean and atmosphere in the far north.
- Scientists are still debating the physical drivers behind this process, and it's an area of active research.