It’s getting more expensive by the moment to buy a home in America. Mortgage interest rates, historically low during most of the pandemic, are rising faster than they have in decades.

more than 8 percent in just one month. That spike, shown above, points to an entirely new and unpredictable phase in what has been a jaw-dropping housing market.

soaring now, too. That means the alternative to buying isn’t particularly appealing, either. And in a time of high inflation, buying a home — and locking in today’s monthly payment for the next 30 years — is a good way to shield yourself from rising rents. In a context of 8 percent annual inflation, a 4.5 percent mortgage interest rate is actually a decent deal.

For would-be home buyers, “the alternative is both the rental option, as well as the option of where do you put your money?” said Arpit Gupta, a professor at N.Y.U.’s Stern School of Business. During past periods of high inflation, real estate has tended to be a better asset than other kinds of investments like stocks (and better than leaving money in a checking or savings account).

Mr. Gupta warns that rising rates can also make rental inflation even worse, because it pushes more people out of the buyer market and into the rental market, driving demand there. In a kind of feedback loop, those ever-rising rents will also continue to put pressure on people who can afford to buy instead, even at higher interest rates.

reached a record, and list prices in the past week are still setting new highs.

“I don’t see a lot of concern from my buyers,” said Beth Abeita, a Redfin real estate agent in Austin, Texas, where home prices rose an astounding 30 percent in 2021. If anything, she said, she hears people worried about the stock market, not mortgage rates — both because they now believe housing will be a better investment, as Mr. Gupta suggested, and because lower stock prices mean some buyers will have less money for a down payment.

There’s a logic to going all-out in bidding for scarce housing right now before it gets worse, Ms. Abeita said.

“Interest rates are not going to rise any longer for you,” she said of those who have secured a house. “You’re not going to pay even higher prices in three months. What you think you’re overpaying for today will be a deal in a few months because everything is increasing so rapidly.”

That touches on another reason that demand probably isn’t cooling yet: The expectation of higher rates to come may drive a surge in buyers trying to get ahead of them now.

In this environment, buyers are also still competing for historically tight supply. The inventory of homes for sale has been at record lows, with more owners holding onto homes as rental investments instead of selling them, and with potential sellers who are afraid they won’t find their next home not entering the market. Higher rates will probably deter some sellers, too, as they choose to stay put in a home recently refinanced at rock-bottom rates rather than move to a new home at an interest rate twice as high.

Exacerbating all of these challenges, there has been underbuilding in the U.S. for years, particularly in expensive coastal metros where housing is in high demand.