All the spare parts appear to be coming together to create what forecasters are calling "Frankenstorm" - a monster combination of high wind, heavy rain, extreme tides and maybe snow that could cause havoc along the East Coast of the US just before Halloween next week.
Hurricane Sandy, having blown through Haiti and Cuba on Thursday (local time), continues to barrel north. A wintry storm is chugging across from the West. And frigid air is streaming south from Canada. And if they meet on Tuesday morning (local time) around New York or New Jersey - which forecasters are predicting - they could create a big wet mess that settles over the nation's most heavily populated corridor and reaches as far inland as Ohio.
With experts expecting at least US$1 billion in damage (NZ$1.2b), the people who will have to clean it up aren't waiting. Utilities are lining up out-of-state work crews and cancelling employees' days off to deal with the power outages.
From county disaster chiefs to the federal government, emergency officials are warning the public to be prepared and President Barack Obama was briefed aboard Air Force One.
"It's looking like a very serious storm that could be historic," said Jeff Masters, meteorology director of the forecasting service Weather Underground.
"Mother Nature is not saying 'trick-or-treat'. It's just going to give tricks."
National Oceanic and Atmospheric Administration forecaster Jim Cisco, who coined the nickname Frankenstorm, said: "We don't have many modern precedents for what the models are suggesting."
Government forecasters said there is a 90 per cent chance - up from 60 per cent two days earlier - that the East will get pounded starting on Sunday and stretching past Halloween on Wednesday.
Things are expected to get messier once Sandy, a very late hurricane in what has been a remarkably quiet season, comes ashore, probably in New Jersey.
Coastal areas from Florida to Maine will feel some effects, but the storm is expected to vent the worst of its fury on New Jersey and the New York City area, which could see 130mm of rain and gale-force winds close to 164kmh.
Eastern Ohio, southwestern Pennsylvania, western Virginia and the Shenandoah Mountains could get snow.
And the storm will take its time leaving. The weather may not start clearing in the mid-Atlantic until the day after Halloween and November 2 in the upper Northeast, Cisco said.
"It's almost a weeklong, five-day, six-day event," he said from a NOAA forecast centre in College Park, Maryland.
"It's going to be a widespread, serious storm."
It is likely to hit during a full moon, when tides are near their highest, increasing the risk of coastal flooding.
And because many trees still have their leaves, they are more likely to topple in the event of wind and snow, meaning there could be widespread power outages lasting to Election Day.
Eastern states that saw blackouts that lasted for days after last year's freak Halloween snowstorm and Hurricane Irene in late August 2011 are already pressuring power companies to be more ready this time.
Asked if he expected utilities to be more prepared, Massachusetts Governor Deval Patrick responded: "They'd better be."
Jersey Central Power & Light, which was criticised for its response to Irene, notified employees to be ready for extended shifts.
In Pennsylvania, PPL Corp spokesman Michael Wood said: "We're in a much better place this year."
Some have compared the tempest to the so-called Perfect Storm that struck off the coast of New England in 1991, but that one didn't hit as populated an area. Nor is this one like last year's Halloween storm, which was merely an early snowfall.
"The Perfect Storm only did US$200 million of damage and I'm thinking a billion," Masters said.
"Yeah, it will be worse."
As it made its way across the Caribbean, Sandy was blamed for at least four deaths in Haiti and Jamaica.
The 18th named storm of the Atlantic hurricane season hit the Bahamas after cutting across Cuba, where it tore roofs off homes and damaged fragile coffee and tomato crops.
Norje Pupo, a 66-year-old retiree in Holguin, was helping his son clean up early Thursday after an enormous tree toppled in his garden.
"The hurricane really hit us hard," he said.
"As you can see, we were very affected. The houses are not poorly made here, but some may have been damaged."