Mortgage rates hit 7% the week the Federal Reserve raised interest rates for the first time in more than three years. On Key Biscayne, where the median home sells for roughly $2.5 million, the jump lands hard.

The Fed's quarter-point hike on Sept. 16 lifted the federal funds target rate to 3.75% to 4%, Reuters reported. It was the first increase since July 2023. The average 30-year fixed mortgage rate reached 7% that same week, according to the National Association of Realtors. By the day before the decision, Mortgage News Daily pegged top-tier rates at 7.22%, the highest since January 2025.

That six-day run-up of 0.33 percentage points was the sharpest spike since October 2024, the rate tracker noted.

Deficit and oil prices push rates higher

Lawrence Yun, the association's chief economist, pointed to oil-price shocks and the federal deficit as drivers. "The whopping, still-growing federal deficit does not help, as more government borrowing means less capital available for the private sector, including for mortgages," Yun said in a statement issued the day of the hike. He called 7% the "new normal" for now.

Average rates rose from 6% in late February to 7% by mid-September, association data show. The last time rates dipped below 6% was Feb. 26, shortly before the Iran war began, when the weekly average briefly touched 5.98%, the Miami Herald reported.

Cash buyers cushion Key Biscayne's high-dollar market

Key Biscayne's price tags amplify even small rate moves. Houses in the 33149 ZIP code were selling for $1,040 per square foot on average in early 2026, a 27% jump from a year earlier, based on Redfin data cited in a June market analysis. Median single-family prices run from the upper $3 millions to about $4 million. Active listings carried a median asking price of $2.62 million as of April, with average list prices for houses near $10 million, InvesTeam Realty data updated in July show.

Island homes were averaging 72 to 183 days on market and selling for about 93% of list price, InvesTeam found.

One buffer: Cash buyers dominate the upper end of the Miami luxury market, meaning many Key Biscayne transactions bypass mortgage rates entirely, the same analysis noted. Miami-Dade County sales of houses above $1 million rose 21% year over year in the first quarter of 2026, from 164 to 199 transactions, according to the Miami Association of Realtors.

Still, the Herald described a market dividing along buyer type. International buyers are snapping up new condos while domestic purchasers chase houses and resort-style properties.

Boat loans climb as Fed signals more hikes

For Key Biscayne's marine economy, the pressure is sharper. The average boat loan rate stood at 8.34% in the second quarter of 2026, with offers ranging from about 7.3% to more than 10% depending on credit, LendingTree data show.

Fed officials signaled more tightening ahead. Projections released alongside the decision showed 16 of 19 policymakers expect at least one more hike before year-end, which would push the short-term rate to about 4.1%. The median inflation forecast for 2026 stands at 3.7%, and officials do not expect to return to their 2% target until 2029.

Fannie Mae now projects mortgage rates will hold in the 6.3% to 6.4% range through at least the end of 2027, well above the 6% the mortgage giant had previously forecast for 2026 and 2027, according to the Herald.