Mother Nature was disguised as winter this Halloween weekend as a rare October nor'easter pummeled northern New Jersey, including Essex County.

Heavy snow fell Saturday for nearly 10 hours, wreaking havoc with traffic, downing trees, causing mass power outages and forcing Gov. Chris Christie to declare a state of emergency.

Alan Reppert, a senior meteorologist with AccuWeather.com, said the storm dumped at most 7 inches on Essex.

He had snow accumulations for the county's four hardest-hit towns — 7 inches in Verona, 5.3 inches in Cedar Grove, 5.2 inches in West Orange and 4.6 inches in Newark.

The National Weather Service had predicted between 3 and 6 inches of snow in Essex County and as much as 12 inches in other areas of northern New Jersey.

As of 10 p.m. Saturday, utility companies Jersey Central Power & Light and PSE&G reported at least 600,000 people total without power statewide — more than 10,000 in Essex County cities and townships, including the Caldwells, Cedar Grove, Irvington, Maplewood, Millburn, Montclair, Newark, Orange, South Orange, Verona and West Orange. 

Paul Walker, a senior meteorologist with AccuWeather.com, said accrued snow on tree leaves and limbs, combined with high winds, likely resulted in downed power lines, causing the outages.

It's unclear when power will be restored, but a release by PSE&G, which manages a majority of Essex County's power, states, "Customers should be prepared for potentially lengthy outages."

In Newark, the city mobilized its emergency crews and snow removal teams Saturday night to clear fallen trees and wires that littered slushy streets.

Meanwhile, Newark Mayor Cory Booker took to the social networking site Twitter to tell residents to remain indoors, "Please stay in tonight. Road conditions are bad, trees are down and still coming down, power outtages (sic) and more. Be safe, stay home."

Some public transportation in the county came to a halt around 2 p.m. Saturday.

Wire problems and downed trees on tracks forced NJTransit to suspend its train services for the Gladstone, Montclair and Morris & Essex lines, according to Courtney Carroll, a spokeswoman for NJTransit. The agency's website says the suspensions will continue Sunday.

Police and fire departments in at least two Essex County towns responded Saturday to minor accidents and fires, according to officials in Millburn and Newark. No injuries were reported.

Kristina Pydynowski, a senior meteorologist with AccuWeather.com, did not have historical data for Essex County snow accumulations in October, but said Saturday's storm broke Newark's previous record of .3 inches for that month in 1952.

She said most of the snow likely will melt in time for Halloween on Monday since high temperatures in the 40s are expected Sunday.

"Most should be gone when everyone's out trick-or-treating," she said.