WASHINGTON — U.S. long-term mortgage rates fell this week following a sharp rise the week before, making September the most volatile month for the key 30-year loan since March.

Mortgage rates have been running near historic lows, spurring prospective homebuyers, amid an uncertain economic outlook. Mortgage buyer Freddie Mac said Thursday the average rate on the 30-year, fixed-rate mortgage dropped to 3.64% from 3.73% last week. By contrast, the average rate stood at 4.72% a year ago.

A sharply divided Federal Reserve last week cut its benchmark short-term interest rate for a second time this year but declined to signal that further cuts are likely in 2019. The Fed rate influences many consumer and business loans.

The average rate for 15-year, fixed-rate home loans declined this week to 3.16% from 3.21% last week.

Freddie Mac surveys lenders across the country between Monday and Wednesday each week to compile its mortgage rate figures.

The average doesn't include extra fees, known as points, which most borrowers must pay to get the lowest rates.

The average fee on 30-year fixed-rate mortgages rose this week to 0.6 point from 0.5 point.

The average fee for the 15-year mortgage was unchanged at 0.5 point.

The average rate for five-year adjustable-rate mortgages fell to 3.38% from 3.49%. The fee remained at 0.4 point.