More than 70 million Americans have experienced the muggiest start to summer on record, with climate change increasing humidity in the Eastern U.S. An Associated Press analysis shows that parts of 20 states and Washington, D.

Meteorologists warn that the coldest burst of Arctic air this season is coming to put an icy and prolonged exclamation point on America’s winter of repeated polar vortex invasions starting this weekend.

The vast majority of Americans are about to get an extended taste of frigid Siberian weather.

Frigid air that normally stays trapped in the Arctic has escaped, plunging deep into the United States for an extended visit that is expected to provoke teeth-chattering but not be record-shattering.

It's another day of brutally cold temperatures and dangerous wind chills across much of the United States.

It’s another day of brutally cold temperatures and dangerous wind chills across much of the United States.