(CNN) If you think the cold across the Midwest and Northeast is bad now, just wait.

Over the next week there will be two cold waves impacting the eastern half of the country. The first one will bring temperatures of 15 to 20 degrees below normal across the Midwest. The second will be the one for the record books.

Over 20 cities have the potential to break record lows Wednesday and Thursday morning. And, more than 35 cities have the potential to have their coldest high temperature on record Wednesday and Thursday.

This isn't just about records, though. The second cold blast will be very widespread, bringing below freezing temperatures all the way down to Florida. In fact, over 68 million people -- nearly a quarter of the US population -- will have a temperature fall below zero next week. Cities such as Minneapolis and Chicago are not forecast to have a high temperature above freezing for at least the next 10 days.

"Record breaking and potentially historic outbreak of cold still appears to be in the offing for the middle of next week," according to the Chicago National Weather Service. "Greater than normal degree of forecast uncertainty in temperatures, due in large part to models showing all-time records being broken and in some cases shattered."

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