Mortgage rates slipped to their lowest level in three months, according to reports by Freddie Mac (FRE) and Bankrate.com. The average interest rate for a 30-year fixed-rate mortgage (FRM) was 5.12% with an average 0.7 point during the week ending August 20, according to Freddie’s weekly survey. That’s down from 5.29% the week prior. A year ago, Freddie Mac’s survey rate was 6.47%. This week's rate is a three-month low for Freddie's survey. Bankrate.com’s survey of large lenders put the same rate at 5.52% with a 0.36 point, down 15bps from one week ago. One year ago, Bankrate.com’s survey rate was 6.66%. It's a two-month low for the survey. The 15-year FRM rate was 4.56% with an average 0.7 point, down from 4.68% last week and its year-ago rate of 6%, Freddie said. Bankrate.com’s survey had the rate at 4.84%, down 9 bps. Five-year Treasury-indexed hybrid adjustable-rate mortgages (ARM) averaged 4.57% with an average 0.6 point in Freddie’s report this week, down from 4.75% last week and 5.99% a year ago. Bankrate.com said buyers are getting in the market to take advantage of the first-time homebuyer tax credit, especially with its November 30 deadline looming. Frank Nothaft, Freddie Mac vice president and chief economist said the low interest rates are reinforcing the housing market, citing increased home construction and builder confidence. Write to Austin Kilgore.