The value of luxury homes situated on these beaches is rapidly decreasing due to the severe impact of climate change.

• Some of the country's most expensive coastal properties are at risk due to climate change, from Dana Point, California, to Long Island, New York, and Nantucket, Massachusetts.
• An affordable Nantucket home that was listed for $2 million last summer was sold for $600,000 early this year.
• The fall Nor'easter, with its sea level rise and intense rainfall, wiped away 70 feet of the beach it was on, leaving barely a trace.

Coastal real estate is experiencing unprecedented flooding and erosion as sea levels rise and storms intensify, affecting some of the nation's most expensive properties in areas such as Dana Point, California, Long Island, New York, and Nantucket, Massachusetts.

The National Oceanic and Atmospheric Administration (NOAA) predicts an "above-normal" hurricane season this year, with up to 13 hurricanes and 4-7 of them categorized as "major" storms.

Climate change is causing real estate values to decline at a faster rate than anticipated, as shown by various risk models.

A Nantucket home that was listed for $2.1 million last summer sold for $600,000 early this year. A fall Nor'easter caused by sea level rise and intense rainfall erased 70 feet of the beach it sits on.

The Boston Globe reported that the buyer stated that the price significantly reduced the risk.

And it's not the only one.

"According to Shelly Lockwood, a real estate agent on Nantucket, several houses have been sold in the mid-7s and mid-8s, which may seem like a lot of money, but if these houses were not at erosion risk, they would have sold for around 10 or 12 million dollars."

Lockwood recently introduced a seminar aimed at assisting fellow agents in re-evaluating the pricing of homes at risk.

Lockwood stated that it is our obligation to inform clients about the risks, and he was becoming increasingly frustrated because this information was not being conveyed to his satisfaction, as he saw houses being sold and believed it was not worth the risk, as it could potentially fall into the ocean.

Montauk Mess

In Montauk, New York, on the eastern end of Long Island, the community was in a frenzy this winter due to a series of storms that threatened to erode its beaches and damage its multimillion-dollar homes. The water was coming in at an unprecedented speed.

"According to Kay Tyler, executive director of Concerned Citizens of Montauk, the water is no longer subsiding in areas where it used to flood and subside quickly. This is causing concern for a friend who owns a $10 million home in the area, as he is unsure of what to do with it if he sells it, as it will never be worth the $10 million he paid for it."

On the East and Gulf Coasts of the United States, 33 zip codes have a median home value of at least $1 million. In these areas, there are 77,005 properties at significant flood risk, according to models by First Street, a climate risk data and analytics firm. This amounts to roughly $100 billion in potential losses.

Property tax relief?

Nantucket homeowners are seeking the assistance of attorney Chris Farley to lower their property taxes as their home values and the beach erode. Some homes have been reassessed while their neighbors have not.

I believe we've been ignoring the issue," said Farley. "Values have been declining for the past 10 years, but it's only been a recent quiet reduction.

One property on the street and seaside cliff, which Farley pointed to, has an assessment of $2.2 million. Although it hasn't been reassessed recently, two other properties on the same street and cliff have been reassessed - one for $500,000 and one for $250,000. The cliff is eroding badly.

Farley estimated that approximately 12-15 feet of sand has disappeared, as indicated by the exposed geo tubes beneath the cliff. It is necessary to cover these tubes with sand.

The home's value has been affected by the loss of access to the waterfront, as the original stairway has disappeared and there is no longer a way to walk down the steps.

Buried in sand

The rising ocean on a Nantucket beach has caused sand to bury two homes, exposing their septic systems and utility wires. As a result, the town must condemn the properties, according to Lockwood.

"This is not what happened last fall. This has happened so quickly," she remarked.

John Conforti, a homeowner, resides adjacent to two homes. The sand has accumulated to such an extent that it now covers his entire front yard. His deck, which previously had a stairway leading to the yard, is now at the same level as the sand. John has owned his home for 42 years and has already relocated it from the beach once.

It's unbelievable what's happened," said Conforti, "and we all agree it's not over yet.

If climate change did not pose new risks to Conforti's home, Lockwood believes that its value would be approximately $2.5 million.

She said, "I'm not sure if it could be sold. Perhaps for five or $500,000, but it would require a buyer willing to lose it."

If property taxes decrease due to declining home values, the local economy may suffer, potentially leading to an increase in taxes for all residents to cover the shortfall.

On Nantucket, residents are deciding which areas of the island require the most assistance and who will be responsible for funding it. Meanwhile, in Montauk, experts are reevaluating coastal resilience plans created almost a decade ago following Superstorm Sandy, as they are no longer effective due to climate change.

— CNBC producers Erica Posse and Dardan Pula contributed to this piece.