* Chicago, Midwest take biggest punch
* More than 5,000 flights canceled
* Hundreds of thousands without power
* Some auto plants closed
* Wall Street trading not affected (Adds companies closed, power outages, slow)
By Mary Wisniewski
CHICAGO, Feb 2 (Reuters) - A huge winter storm pummeled the United States on Wednesday, bringing parts of the Midwest to a standstill, delivering another wintry swipe to the Northeast, and disrupting businesses, flights and other transport.
Major automakers shut down plants in six Midwestern states and Ontario.[ID:nN02208893]. The storm also paralyzed grain and livestock movement.
The storm, touching some 30 states and a third of the U.S. population, stretched from New Mexico to Maine as it moved toward the northeast where an ice storm wreaked havoc on New York City's morning commuters.
Chicago was set to get its biggest snowfall in more than 40 years. Some 20 inches (54 cm) of snow was forecast to pile up by late Wednesday. Snowfalls of a foot (30 cm) or more were recorded from Oklahoma City to Kansas City and Indianapolis.
The website flightaware.com, which tracks airline cancellation information, said more than 5,000 flights had been canceled in the United States so far on Wednesday. That followed thousands of flight cancellations on Tuesday.
Power was out for more than 375,000 customers from Texas to New England, and into Canada. [ID:nN02186033].
Treacherous ice, rather than deep snow, hit New York City. The heavily used commuter rail service between New Jersey and New York was suspended due to ice buildup on the overhead power lines, authorities said.
But Wall Street trading was not impacted by the storm as exchanges opened on time and many traders worked from home.
The huge two-day storm delivered its strongest punch to the Midwest, dumping as much as three inches (7.6 cm) of snow an hour on Chicago during most of the night along with winds of up to 40 miles per hour (65 kph).
CBOT's open-outcry trade opening was delayed by 30 minutes from from the normal time of 9:30 a.m. (1530 GMT), but Globex electronic trading opened on time at 9:30 a.m., said Chris Grams, of the world's largest futures exchange, the CME Group <CME.O> in Chicago. [ID:nN02171198]
Chicago's two major airports canceled a combined 2,000 flights, the city's Department of Aviation said.
Among the storm-affected businesses, large and small, Abbott Laboratories, <ABT.N> a major healthcare company, closed its headquarters north of Chicago on Wednesday.
Major interstate highways in the Plains and Midwest were closed and a state of emergency was declared across the area.
Major railroads, including Burlington Northern Santa Fe and Norfolk Southern, which transport commodities across the United States, said snow and ice was slowing them down.
"The impact is widespread just as the weather conditions are," said BNSF spokesman Steven Forsberg.
'HISTORIC STORM' IN CHICAGO
Chicago's Lake Shore Drive along Lake Michigan was closed as snow drifted over the road.
The third biggest city in the United States could end up with the largest snowfall since 1967, city officials said.
"We will continue to do everything we can to protect the safety of the residents of this city as we deal with the impact of this historic storm," Chicago city chief of staff Ray Orozco told an early morning news conference.
In the Northeast, already facing a wintry mix of snow and sleet, the storm was expected to dump 12-18 inches (30-45 cm) of snow on Boston through Wednesday.
"We have skeletal crew. This weather has been brutal," said John Canally, investment strategist at LPL Financial in Boston.
"Our Boston office is closed, but we are still doing our regular morning routines. Those who couldn't make it in are working remotely from home."
Snow was not the only hazard.
"The thing we're most fearful of is freezing rain. It could turn the roads into ice rinks pretty quickly," Massachusetts Emergency Management Agency spokesman Peter Judge said.
The storm wreaked havoc on agricultural operations, threatening the dormant winter wheat crop and livestock, slowing the processing and transportation of agricultural commodities, and delaying futures markets.[ID:nN02208605]
As the blizzard moved northeast, a dangerous deep freeze followed in its wake from Montana and the mountain states through the Plains and south to Oklahoma.
The storm lost a lot of its force in Canada, but it still sparked snowfall warnings from the maritime provinces along the east coast through to Niagara Falls, in the central province of Ontario.
In Toronto, where forecasters had predicted the worst storm in at least two years, only 10 cm (3.9 inches) of snow had fallen by the morning and the storm was expected to abate by the afternoon.
At Toronto's Pearson International Airport some 300 flights were canceled out of the 1,200 scheduled for the day, most of them to and from major U.S. cities east of Chicago.
SPRING AROUND THE CORNER?
But -- for those who believe in such things -- a rodent predicted on Wednesday that a particularly tough winter will be over soon.
The most famous groundhog in the United States, Punxsutawney Phil, emerged from a tree stump at dawn and, unusually, did not see his shadow, signaling that spring is just around the corner, according to tradition.
The rodent's "prognostication" each Feb. 2 is an annual tradition that was brought to the United States by German immigrants, and is now watched by thousands of people who trek to a Pennsylvania hillside to witness the ceremony.
If the groundhog is judged to see its shadow, tradition holds that there will be six more weeks of winter. [ID:nN02190948] (Additional reporting by Jon Hurdle in Philadelphia, Ryan Vlastelica and Ellen Wulfhorst in New York, Carey Gillam in Kansas City, Ros Krasny in Boston and Pav Jordan in Toronto; Writing by Jackie Frank; Editing by Frances Kerry)
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