This was the least affordable week to buy a home in 35 years

• Housing affordability reached a new low as mortgage rates spiked while home prices remained high.
• The payment-to-income ratio for a home hit a 35-year high, real-estate data firm Black Knight said.

Combine stubbornly high home prices with spiking mortgage rates, and you get the least affordable week for the US housing market in 35 years.

The average rate for a 30-year fixed-rate mortgage hit a new pandemic-era high, jumping to 5.89% for the week ended Thursday, according to Freddie Mac. Buyers face hefty mortgage payments that eat up more of their incomes and make it tougher for them to afford homes, even if the overall market is cooling.

A homebuyer making the median US income would need to fork over 35.1% of their earnings each month to pay the principal and interest on a median-priced home of roughly $400,000, assuming they have a 30-year mortgage and put 20% down, according to a new report from Black Knight, a mortgage technology and data provider.

That payment-to-income ratio has reached its highest point in 35 years, eclipsing a previous high set in June, according to Black Knight. Personal finance experts don't recommend spending more than one-third of your monthly income on housing.

To give you a sense of how mortgage-rate changes can affect what you pay per month for a home, here's an example: Let's say you buy a house for $425,000 and put 5% down.

If you bought a year ago and got a 30-year mortgage at 2.88%, the average at the time, you'd be paying roughly $1,676 per month, according to Insider's mortgage calculator. But if you obtained the same mortgage for the same house today, and put 5% down, the monthly payment would be $2,392 based on a rate of 5.89%.

Multiply that over 30 years, and the additional cost would be $257,760.

There's a silver lining for buyers, however

The good news for buyers is homes can't remain this unaffordable forever, according to Andy Walden, Black Knight's vice president of enterprise research.

When mortgage rates rise like this, more buyers back out of the for-sale market, which translates to less demand for homes. With fewer buyers competing for homes, sellers may be forced to cut their prices in order to reach a deal. Other sellers are considering renting out their homes instead, since the market for rentals remains comparatively strong.

In a handful of US cities such as Seattle, Los Angeles, and Denver, previously hot housing markets appear to be giving way to falling home prices. Data from the S&P Dow Jones Indices, published late last month, showed price growth turning negative in six major metropolitan areas from May through June.

"Given the large role affordability challenges appear to be playing in shifting housing market dynamics, the recent pullback in home prices is likely to continue," Walden said in a statement.

The median home price in July was $412,547, up 7.4% from a year ago, according to the brokerage Redfin. But that marked the second straight month-over-month decline from a peak in May of roughly $430,000.