LOS ANGELES (AP) — The average rate on a 30-year mortgage climbed this week to its highest level in more than five months, pushing up borrowing costs for prospective homebuyers in what’s typically the housing market’s busiest stretch of the year.

The rate rose to 7.22% from 7.17% last week, mortgage buyer Freddie Mac said Thursday. A year ago, the rate averaged 6.39%.

When mortgage rates rise, they can add hundreds of dollars a month in costs for borrowers. That limits how much homebuyers can afford at a time when a relatively limited number of homes on the market coupled with heightened competition for the most affordable properties has kept prices marching higher.

The average rate on a 30-year mortgage has now increased five weeks in a row. It hasn’t been this high since November 30.

Borrowing costs on 15-year fixed-rate mortgages, popular with homeowners refinancing their home loans, also rose this week, lifting the average rate to 6.47% from 6.44% last week. A year ago, it averaged 5.76%, Freddie Mac said.