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What is a nor'easter?
01:03 - Source: CNN
CNN  — 

The governors of New Jersey and New York have each issued a state of emergency in advance of an anticipated nor’easter this week.

In New York, Gov. Kathy Hochul declared the emergency for more than 20 counties.

“I am proactively declaring a State of Emergency to ensure we can provide the necessary resources to respond to this storm and protect lives and property in regions where the forecast is calling for significant rainfall,” Hochul said in a news release. “I am encouraging New Yorkers to prepare now for inclement weather expected over the coming days and urging commuters to take precaution ahead of heavy rainfall expected tomorrow morning.”

Hochul directed various state agencies earlier Monday to prepare assets for deployment to impacted regions.

New Jersey’s state of emergency began at 8 p.m., Gov. Phil Murphy said.

“Severe weather conditions will impact the state starting tonight through the next several days,” he said.

The National Weather Service has issued several flash flood watches in the northeast beginning Monday evening and lasting through Tuesday afternoon that impacts nearly 30 million people.

Lines of training thunderstorms are likely to develop, producing widespread totals of 2 to 5 inches, with higher amounts possible.

Rainfall rates will exceed 1 inch per hour at times.

This rainfall will lead to flash flooding of creeks, streams, urban areas and poor drainage areas where the rain is the heaviest.

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What is a nor’easter?

A nor’easter is a storm along the East Coast with winds typically coming from the northeast, according to the National Weather Service. The storms can occur at any time of year but are most common between September and April.

In winter, temperatures associated with a nor’easter can be much more extreme than in the fall, which can lead to more intense storms and snow. The storms can cause beach erosion and rough ocean conditions, with winds of 58 mph or more.

The Metropolitan Transportation Authority, which oversees the New York City subway and other transit lines, is expecting 6 inches of rain over 12 hours, but it will be nothing like Hurricane Ida.

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“At no point do we expect to see the type of intense rainfall over a very short term that we had during Hurricane Ida,” MTA’s acting Chair and CEO Janno Lieber said, noting the city saw more than 3.5 inches in one hour during Ida.

“But, we are prepared for whatever comes,” Janno added.

The biggest issue and constraint the MTA faces is the city sewers, which can be overwhelmed as they were during Ida, Janno said, but they don’t expect it to be an issue during the storm.

CNN’s Gene Norman, Rob Frehse and Kiely Westhoff contributed to this report.