NEW YORK — U.S. stock trading will be closed on Monday and possibly Tuesday in response to Hurricane Sandy, NYSE Euronext said late on Sunday.

NYSE Euronext, which runs the New York Stock Exchange, had previously said that electronic trading would remain open and that only the exchange's trading floor would close.

In a statement, the company said that "the dangerous conditions developing as a result of Hurricane Sandy will make it extremely difficult to ensure the safety of our people and communities, and safety must be our first priority."

Nasdaq said it would also close all U.S. equity and derivatives exchanges, as well as the Nasdaq/FINRA TRF on Monday, CNBC reported late Sunday night. It is likley the markets will also be closed on Tuesday, according to the statement from the exchange.

Hurricane Sandy is expected to slam into the U.S. East Coast on Monday night, bringing torrential rains, high winds, severe flooding and power outages. The rare "super storm," created by an Arctic jet stream wrapping itself around a tropical storm, could be the biggest to hit the U.S. mainland, forecasters said.

The scramble on Wall Street started early as New York Governor Andrew Cuomo announced the subway, bus and rail system in the city begin to close at 7 p.m. EDT on Sunday.

About 8.5 million commuters utilize the Metropolitan Transit Authority's transit lines daily, meaning most Wall Street employees would be unable to get to work. New York City Mayor Michael Bloomberg also closed public schools and ordered an evacuation of 375,000 people in coastal areas, including downtown offices of banks such as Citigroup.

Wall Street was spared the worst of Hurricane Irene in August last year. Officials had feared Hurricane Irene would flood lower Manhattan and cripple business in the world's financial capital, but the flooding was minor and there were no major disruptions at the exchanges.

Storm Tracker: Live interactive map of Hurricane Sandy

Muted trading

CME Group Inc said it was suspending floor trade on Monday at NYMEX headquarters, the world's biggest oil and energy futures and options market. But electronic trade at all of CME will open at their regularly scheduled time at Globex and ClearPort, CME's online electronic platforms.

The Securities Industry and Financial Markets Association said it is recommending an early close of noon EDT on Monday for the trading of U.S. dollar-denominated, fixed-income securities. It said its member firms should decide for themselves whether their fixed-income departments remain open for trading.

One bond trader at a large Wall Street firm said the New York-based banks would route orders through their Midwest and West Coast offices. West Coast employees were planning to get up early, he said, while colleagues in Europe were expecting a long working day on Monday.

Volumes were, however, expected to be lower and orders may be harder to fill, the trader added.

Ken Polcari, managing director for ICAP Equities, said early on Sunday: "The word going around the floor on Friday was people should expect this to happen. In the event the exchange does not open, they will trade electronically though."

"If that happened, it's probably going to be very muted volume," he added.

Working from home

Goldman, whose office in lower Manhattan is in one of the areas to be evacuated, told employees that it would open for business, with some staff working from offices in Greenwich, Connecticut and in Princeton, New Jersey.

It also plans to use teams in London and other locations around the world for additional support.

Citigroup has its trading floor near the Hudson River in the Tribeca neighborhood in Manhattan, putting it in a flood zone. The bank is operating from a backup trading floor in New Jersey and will shuttle critical employees there as necessary. It said "non-critical personnel should invoke their work-from-home strategies."

Credit Suisse Group is situated by Madison Square Park in New York, outside of the city's evacuation zones for hurricanes. The Swiss bank planned to open its trading floor as usual on Monday, staffed with employees that live nearby and key personnel that can access trading systems remotely.

A JPMorgan spokeswoman said many of the bank's traders lived in Manhattan and will be in the office on Monday. The bank expects to be fully operational, using backup trading and technology from Europe or Asia as needed, she said.

Wells Fargo & Co , which has about 1,170 locations in Sandy's path, had already closed some locations by Sunday afternoon. Executives in various departments were holding conference calls on Sunday to discuss preparations, a bank executive said.

The executive also said the exchanges' plan to stay open on Monday had complicated banks' preparations.

"With MTA shut down, how are people supposed to get around?" the executive asked.

Plan to stay open

The NYSE has not suffered a weather-related late opening since 1996, having opened on time in extreme circumstances in the past, including Hurricane Irene last year. It last suspended physical trading floor operations on Sept. 27, 1985, due to Hurricane Gloria, during which all markets were closed. The NYSE was closed for three days after the September 11, 2001 terrorist attacks on the nearby World Trade Center buildings.

The Big Board is located in Zone C, an area whose likelihood of evacuation is relatively low, according to the New York Office of Emergency Management.

The NYSE has arranged accommodations for essential staff near its lower-Manhattan headquarters, while other employees have been encouraged to work from home or alternate locations, said a person familiar with the situation.

Being on site is more important for traders that rely on fast network connections and real-time market information, than bankers such as deal advisers and private equity firm executives.

Blackstone Group , for example, planned to close its office on Monday.

Hurricane Sandy also led to some events being canceled or postponed. Citigroup Prime Brokerage postponed a hedge fund event that had been scheduled for Tuesday.

CNBC contributed to this report.

More business news:

Follow NBCNews.com business on Twitter and Facebook