The NWS is forecasting a low temperature in Chicago of minus 20°F on Wednesday morning. This would set a daily record low, and be one of the coldest temperatures ever recorded in the city. The last time it was this cold in Chicago was the period from Jan. 18-20, 1994, the Weather Service said.

A low of minus 20°F would be within 7°F of the city’s all-time coldest temperature, which was set in Jan. 1985.

If Chicago’s high temperature remains below minus 11°F on Wednesday, it would be the city’s coldest afternoon high temperature on record. In fact, the city could see temperatures remain below 0°F for 60 hours or so, a rarity even for such a cold location.

About 200 million people in the U.S. will see temperatures dip below freezing during the coming week, based on model projections.