AUSTIN, Texas (AP) — Another winter storm front is blowing through the nation’s midsection, where power grids haven’t adjusted for the wild weather swings that come with climate change. More than 100 million people live in areas covered Wednesday by some type of winter weather warning, watch or advisory. Millions remain without power in the record-breaking cold, mostly in Texas. At least 20 people have died. Blame the polar vortex. The weather pattern usually keeps to the Arctic, but it’s increasingly visiting lower latitudes and staying beyond its welcome. Scientists say global warming caused by humans is partly responsible for the polar vortex’s southward escapes becoming longer and more frequent.