Who the heck can tell what's up with the real estate market these days? It's clear that home prices aren't flying upward the way they were a year or two ago. But is that just an overheated market returning toward sanity, or the first sign of a bigger decline? Nobody really knows.

What is clear, though, is that some places are seeing home values weaken more than others, and for reasons that suggest a systemic problem rather than a short-term market correction. In many cities, more than a quarter of mortgages are "underwater"--that is, the homeowners owe more on their mortgages than they could get by selling their homes. Vacancy rates are high, which may mean that too much supply will force prices downward for both renters and buyers. And a larger-than-average percentage of homeowners are either in foreclosure or delinquent on their mortgage payments, suggesting both a weakening local economy and a likelihood that these homes will soon come on the market at bargain prices.

The helpful folks at personal finance site GOBankingRates have compared all these numbers and come up with a list of 40 U.S. cities that seem in danger of a housing crash. If you're considering buying a home in one of these towns, it might be smart to wait at least a few months.

You can find the full list here. These are eight of the cities where the dangers of a housing crash seem greatest:

1. Newark, New Jersey

This year, for the first time since 2015, the median price of a Manhattan apartment slipped below $1 million, though only barely. So it makes sense that cities where housing prices were driven up by buyers who could not afford New York City are now seeing their real estate markets weaken in tandem with New York's.

That may be what's happening in Newark. The median home value is $252,000, and 27.9 percent of Newark homes are underwater. More than 6 percent of homeowners are behind on their mortgage payments. Vacancy rates are higher than the national average as well.

2. Detroit-Warren-Dearborn, Michigan Metropolitan Area

Detroit struggled back from bankruptcy five years ago, but still tops the nation in both childhood and adult poverty, according to a new report by WalletHub. Meantime, after the city restored such services as street cleaning and lighting that had disappeared during its downward economic spiral, there was a bit of a building boom, which may have put some pressure on housing prices.

Today, 34.4 percent of homes in the Detroit metro area are underwater on their mortgages, the highest percentage in the nation--even though the median price of a Detroit home is only $161,300, according to Zillow. And percentage of homes underwater is the surest sign of a housing market on the decline, GOBankingRates says.

3. Bridgeport, Connecticut

Connecticut's economy of the past few years has been described as a "meltdown" by a local paper, and Bridgeport is currently hanging its hopes on state approval for MGM Resorts to build a long-awaited casino in town. That may actually go forward this year.

In the meantime, 26.9 percent of homes here are underwater, and foreclosure and delinquency rates are high as well. The future of the real estate market here may depend on whether and when the casino is built.

4. Baltimore

As more than one local observer has noted, Baltimore, which is majority non-white, suffers from a huge economic disparity between its white and non-white residents. As it's struggled with this disparity and the local economy in general, other state residents have turned away from this city, so that in a recent poll, two thirds of Marylanders say Baltimore is no longer the state's economic engine. That distinction may belong to the Maryland towns closer to Washington, D.C., especially now that Amazon is putting its second headquarters into nearby Northern Virginia.

Even though its median home cost is only $119,200, more than a quarter of Baltimore's homes are underwater on their mortgages. And its homeowner vacancy rate (i.e. empty homes for sale) is 4.4 percent, more than twice the national average.

5. Hartford, Connecticut

Aetna planned to move its headquarters to New York City, a plan that was quashed last year after CVS acquired the insurer. That's good news for Hartford's struggling economy, but not good enough. More than 22 percent of homeowners here are underwater on their mortgages. Homeowner vacancy rates are 4.3 percent, and rental vacancy rates are also very high, at 9.2 percent. (This affects home prices because when there is plenty of attractive, affordable rental housing, people may choose to rent instead of buy.)

6. Paterson, New Jersey

Paterson is called "Silk City" for its one-time importance in the silk industry, but those glory days are more than a century in the past. Today, it's known as a destination for immigrants who can't afford nearby New York City. It has an unemployment rate of 7.7 percent.

Paterson's median home price of $253,100 is the highest on this list, but even so, 24.7 percent of the city's mortgages are underwater. The payment delinquency rate of 3.6 percent is three times the national average as well.

7. Cleveland

Cleveland's economy has consistently lagged behind the rest of the nation during the last few years of recovery, and a local effort to turn it into a hub for blockchain-related startups (called "Blockland") hasn't delivered as hoped.

Cleveland's median home price is only $55,900, and 25.9 percent of its homes are underwater on their mortgages. Not only that, one out of every 832 homes in Cleveland is in foreclosure, the highest foreclosure rate on this list.

8. Fayetteville, North Carolina

Home to Fort Bragg, Fayetteville benefits from a strong military presence and defense sector. Still, the city is plagued by poverty compared with other cities its size, with one in four local children living below the poverty line. It has a median home price of $108,100, and 26.8 percent of its homeowners are underwater on their mortgages.

9. Dayton, Ohio

Manufacturing is core to Dayton's economy, and the city has suffered as GM closed several local plants over the years. Newer factories offer lots of jobs, but at substantially lower wages than the GM plants did. Without attractive jobs, people are leaving, with Montgomery County's population shrinking by more than 1 percent since 2010, while the nation at large saw its population grow by 5 percent.