The polar vortex brought disruption to air traffic and morning commutes, warnings of wind chills and frostbite, and brutally cold temperatures across a large portion of the United States.

In parts of the Midwest, temperatures reached as low as 40 degrees below zero and Chicago’s O’Hare International Airport canceled half of its flights because fuel supplies froze, Reuters reported.

At least four deaths were blamed on the frigid weather, including a 48-year-old man from Chicago who died of a heart attack shortly after shoveling snow and an elderly Indianapolis woman who was found outside her home.

Just what do these cold temperatures look like? Here are a few photos showing the effects of the polar vortex:

Icy Lake Michigan Ice builds up along Lake Michigan at North Avenue Beach as temperatures dipped well below zero in Chicago. Woman Falling NYC A woman falls on ice in Manhattan. Photo: Reuters Charles River Birds gather by the partially frozen river in Boston. Photo: Reuters Gust Of Snow Chicago A woman walks through a gust of blowing snow in Chicago Photo: Reuters Detroit Truck Barry Tilton cleans the snow off of his pick-up truck in the midtown neighborhood of Detroit, Michigan January 6, 2014. Photo: Reuters Indianapolis Snow Plow Snow plows rumble through the streets of Indianapolis. Photo: Reuters Indianapolis dogs A couple walk their dogs on a snow-covered Indianapolis street. Photo: Reuters Indianapolis A man clears snow from his car in Indianapolis. Photo: Reuters Chicago Bus Shelter. A person walking in a Chicago bus shelter during the polar vortex. Photo: Reuters Homeless Man Polar Vortex A homeless man sleeps on an icy street. Aerial View Chicago An aerial view of an icy and cold Chicago