Update: Four counties in Massachusetts are under flood warning on Friday

At 3:22 p.m. on Thursday, the National Weather Service issued an updated flood warning for the coastal areas of Essex, Plymouth, Barnstable and Nantucket, effective Friday between 11 a.m. and 6 p.m.

“One to two feet of flooding above ground level is possible in low-lying areas near shorelines and tidal waterways,” the weather service says. “The greatest risk of moderate flooding is along the Plymouth coast, including the north shore of Cape Cod (Bay Side), from Sandwich to Dennis.”

“At high tide, some coastal roads will become impassable. Flooding of 12 to 24 inches will affect roads on the North Shore from Salem and Marblehead through Gloucester to Newburyport. Heavy surf will cause beach erosion and throw debris onto coastal roads. Many roads near Nantucket Harbor will become impassable at 12 to 24 inches of water, affecting access to ferry terminals. These include Easy Street, South Beach Street, Easton Street, Walsh Street, Willard Street and Straight Wharf. Roads will remain passable. Shallow flooding of less than 12 inches will affect low-lying areas in Provincetown, primarily near the airport and Race Point Road. In Truro, flooding of up to 12 inches will affect low-lying areas near Pamet Harbor and along the Pamet River. Hazardous conditions for swimming and surfing and localized beach erosion,” the weather service adds. “If you must travel, allow extra time as some roads may be closed. Do not drive around barriers or through waters of unknown depth. Take necessary steps to protect property at risk of flooding. Inexperienced swimmers should not enter the water due to dangerous surf conditions.”

Deciphering advisories, observations and warnings: Understanding weather warnings

• Flash flood warning: take action!

A flash flood warning is issued when a flash flood is imminent or is already occurring. In areas at risk of flooding, it is important to get to higher ground immediately. A flash flood is a sudden and severe flood that can develop within minutes to hours and can occur even in areas where there is currently no rainfall.

• Flood warning: take action!

A flood warning is issued when flooding is imminent or already underway.

• Flood warning: Please note:

A Flood Warning is issued when flooding is not expected to reach a level of severity that would warrant a warning. However, such a warning may cause significant inconvenience and, if ignored, may result in situations threatening life and/or property.

• Flood warning: Be prepared:

A flood warning is issued when conditions are favourable for flooding. This does not mean that flooding will occur, but it is possible.

Braving the storm: Advice on flood protection from the weather service

In flood-prone regions or when camping in low-lying areas, understanding and following the weather service’s flood safety guidelines can be life-saving:

Move to higher ground:

If you are in a flood-prone area or camping in a low-lying area, the first step is to move to higher ground.

Follow the evacuation instructions:

If local authorities issue an evacuation order, obey it immediately. Secure your home by locking it before leaving.

Disconnect utilities and equipment:

If time permits, unplug your utilities and appliances. This will reduce the risk of electrical hazards during flooding.

Avoid flooded basements and flooded areas:

Avoid basements or rooms in contact with water where there are electrical outlets or cables. Preventing electrical accidents is crucial.

For safety reasons, evacuate immediately:

If you notice sparks or hear buzzing, crackling, popping or banging noises, evacuate immediately. Do not enter water that may be live.

Stay away from floods:

Never attempt to walk through flood water, even if it appears shallow. Even 6 inches of fast-flowing water can sweep you off your feet with full force.

Seek higher ground if you are trapped:

If you become trapped in running water, go to the highest possible point and call 911.

Heavy rain can create a risk of flooding, especially in low-lying and flood-prone areas. Never attempt to drive through water on the road, no matter how deep it appears. According to the weather service, as little as 30 cm of water can sweep away most vehicles. Stay safe by being prepared and informed.

Advance Local Weather Alerts is a service from United Robots that uses machine learning to compile the latest data from the National Weather Service.