U.S. mortgage rates dropped to a record low, smashing through a previous record set earlier this year, a closely watched mortgage survey showed Thursday.

The lowest mortgage rates in decades and high affordability have also helped the hard-hit housing market find some footing this year after a three-year slump.

Interest rates on U.S. 30-year fixed-rate mortgages, the most widely used loan, fell for a fifth consecutive week, averaging 4.71 percent for the week ending Dec. 3, down from the previous week's 4.78 percent, according to a survey released on Thursday by home funding company Freddie Mac.

Freddie Mac, the second-largest U.S. mortgage finance company, started the survey in 1971.

Mortgage rates are linked to yields on Treasuries and yields on mortgage-backed securities.

The sharp drop in rates provides an opportunity for consumers, who may want to spring into action, if forecasts by economists ring true.

Cameron Findlay, chief economist at LendingTree.com in Charlotte, North Carolina, said mortgage rates will be sharply higher next year.

Findlay expects yields on 10-year Treasuries to be at about 3.84 percent by the second quarter of 2010, with a 180 basis points spread between mortgages and Treasuries.

That would translate into a 5.64 percent 30-year fixed-rate mortgage, significantly higher than current levels.

"Low mortgage rates and the cumulative decline in house prices have contributed to an extremely affordable housing market and helped spur home sales this year," Freddie Mac vice president and chief economist Frank Nothaft said in a statement.