Most of the Great Lakes surface has frozen for the second consecutive winter.

Nearly 81% of the lakes’ surface area was covered with ice, the NOAA Great Lakes Environmental Research Laboratory reported on February 20.

That was down slightly from more than 85% on February 19.

Temperatures have plunged this month, nearly doubling over the past couple of weeks.

Records show the lakes’ most widespread freeze was 94.7% in 1979. The ice cover topped out at 92.2% in March 2014.

The ice blanket reaches across more than 90% of Lakes Superior, Huron and Erie, while Lakes Michigan and Ontario are more than halfway covered.

It has produced some spectacular visual images, from ice caves along the Lake Michigan shoreline to a glacial buildup making it appear that Niagara Falls had frozen in place.

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