Winter Storm Linus brought a swath of heavy snow across much of the Northeast Monday, disrupting the start of the workweek for millions of people. The storm also laid down a narrow zone of freezing rain across a heavily populated area near New York City into parts of southern New England.

Now, a flash freeze is starting to take its toll on Tuesday's commute. in the Boston area, and 10-20 minute delays were also reported on MTA trains from Long Island.

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A winter weather advisory is in effect for areas from southern Connecticut to Delaware, including New York City and Philadelphia until 9 a.m. as cold morning temperatures have frozen any standing water and slush on untreated roads, parking lots and sidewalks. Even roads treated with salt or chemicals may be vulnerable as temperatures could reach levels too low for those treatments to be effective.

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Linus has a history of prolific snowfall. It brought Detroit its third-heaviest snowstorm on record, and Chicago saw more than a foot and a half of snow.

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Snow officially began at Central Park in New York City at 8:47 p.m. EST Sunday. After snowing all night, precipitation mixed with and changed to rain for a few minutes just before 6 a.m. Monday, but quickly changed to freezing rain by 5:54 a.m. Freezing rain with occasional sleet continued the rest of the morning, but Central Park changed back to light snow at 1:41 p.m. Monday.

Snow overspread much of the rest of New York state and New England, and up to 24 inches of snow had already piled up in Massachusetts by evening Monday.

Boston reported 16.2 inches of snow Monday, bringing its total to 40.5 inches over the past seven days. That's the snowiest one-week period in Boston since modern weather records began in 1891.

A narrow stripe of freezing rain accompanied Linus earlier as warm air aloft slid over a below-freezing air mass at the surface over the New York City area, including Long Island, as well as coastal southern New England.

In New England, the heaviest snowfall totals were in a zone from just west and north of Boston to Downeast Maine. Leominster, Massachusetts picked up 20.7 inches, while Woodford, Vermont chalked up 19 inches of snow.

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MORE ON WEATHER.COM: Winter Storm Linus Photos

Pedestrians navigate the snow, ice and puddles along a Manhattan street on Feb. 2, 2015 in New York City. (Spencer Platt/Getty Images)