WASHINGTON — Rates on 30-year mortgages rose for a third straight week, hitting the highest level in more than three months.

Freddie Mac, the mortgage company, reported yesterday that 30-year, fixed-rate mortgages averaged 6.24 percent this week, up from 6.04 percent last week.

That is the highest level since the week of Nov. 15 when 30-year rates also averaged 6.24 percent. It marked a significant reversal from the beginning of the year when 30-year rates dropped below 6 percent for six straight weeks, reflecting a significant slowdown in the economy. That slowdown prompted the Federal Reserve to aggressively cut the short-term interest rate it controls by 1.25 percentage points in January, the biggest one-month cut in this rate by the Fed in more than a quarter-century.

In other rate moves this week, rates on 15-year mortgages, a popular choice for refinancing, rose to 5.72 percent, up from 5.64 percent last week. Rates on five-year adjustable-rate mortgages rose to 5.43 percent, up from 5.37 percent last week.

Rates on one-year ARMs climbed to 5.11 percent, compared to 4.98 percent last week.