As Hurricane Sandy intensified Monday, many local businesses closed early or put in place emergency plans for workers even as others — grocers, hardware stores and some bars and restaurants — juggled an influx of hardy customers.

In Georgetown and Alexandria, where the Potomac River often floods during heavy rains, preparations and closings started early. Sandbags were in front of many storefronts along Union Street in Alexandria by midday Monday, according to Bill Reagan, executive director of the Alexandria Small Business Development Center. Reagan had begun nudging business owners Friday to review their insurance policies, have generators on hand, put computers on backup and test emergency lighting.

“These people are veterans of some really bad weather,” he said. “They know to get stuff off the floor so water can rise, and then went it recedes they can just sweep it out.”

In Georgetown, where the Washington Harbour restaurant and office complex sustained massive water damage last spring, the floodgates were up and construction of a new skating rink was postponed for at least two days. “All the gates are up and everyone is very prepared,” said Julie Chase, a spokeswoman for the complex’s owner.

While many shops were open at the start of the day, private offices emptied earlier, with about three-quarters of them unoccupied as of midmorning, according to the real estate firm CBRE, which manages about 240 buildings between Northern Virginia and Baltimore. The company began fueling generators, clearing drains and securing loose trash cans and benches before the rain began, according to CBRE’s Kathy Allgier.

Sandy's projected rainfall totals

Grocery and hardware stores faced a different problem: how to keep inventory stocked.

By midday Monday, the Costco in Pentagon City, the Target in Columbia Heights, Annie’s Ace Hardware in Petworth and True Value Hardware in Dupont Circle were all out of flashlights and batteries. Supplies of bottled water were gone or running low.

“Gallons, 24-packs, 12-packs, every style of water we had, we sold out by early Saturday evening,” Target store manager Darren Whitlock said. “We got some more in Sunday, but by 10 a.m., we were sold out.”

Late Monday morning, Annie’s Ace received a shipment of 200 sandbags — and sold them in less than 10 minutes. An oversupply of batteries for the Christmas season didn’t last much longer. “They arrived a couple weeks ago and I thought, ‘You might have been overenthusiastic about these batteries,’ ” said owner Anne Stom. “Now I don’t have any . . . it looks like a locust has gone through.”

Giant Food planned to keep normal business hours for all of its 171 stores, said spokesman Jamie Miller. But the chain canceled most Monday and Tuesday delivery orders destined for homes on the East Coast, according to Elana Margolis, spokeswoman for its Peapod delivery service. “Our biggest concern is to keep our drivers safe,” she said.

Hotel managers reported mixed results.

Some experienced cancellations because of shelved vacations or meetings; others expected increased local business resulting from power outages. The occupancy rate at the Sheraton in Reston was 50 percent lower than expected Monday, but Mick Ilagen, a manager at the hotel, said that could change quickly as the storm came ashore and flooding and power problems multiplied.

“The last time this happened, we sold out of rooms in one afternoon,” Ilagen said.

It was much the same at the 836-room Omni Shoreham Hotel in Woodley Park. General manager Pete Fams said several groups canceled visits, but some of the vacancies were offset by people extending their stays because of canceled flights and downtown workers looking to avoid taking to the road as the winds and rain worsened.

In some cases, storms like Sandy are good for business. With so many workers stuck at home and bored, bars and restaurants, particularly in densely built parts of the District, were stocking up on booze and offering hurricane promotions over social media.

The Heights Restaurant and Bar on 14th Street NW bulked up its orders of produce and seafood early this week, while Town Tavern in Adams Morgan, Star and Shamrock on H Street NE, Duffy’s Irish Pub near U Street and others promoted hurricane parties or specials via Twitter or Facebook, even though some closed their kitchens.

The Diner, Tryst and the Coupe, three restaurants owned by Constantine Stavropoulos, were open Monday, partly because he said about 90 percent of his workers live nearby in the District.

“I’ve got some staff that are probably out riding their skateboards in this weather right now,” he said.

Catherine Ho and Steven Overly contributed to this report.