WASHINGTON (AP) — Average long-term U.S. mortgage rates surged this week, marking their largest one-week gain this year.

Mortgage company Freddie Mac says the nationwide average for a 30-year loan jumped to 4.23 percent from 4.12 percent last week. The average for a 15-year mortgage, a popular choice for people who are refinancing, rose to 3.37 percent from 3.26 percent.

At 4.23 percent, the rate on a 30-year mortgage is at its highest level since the week ended May 1, though it is still at a historically low level.

Mortgage rates often follow the yield on the 10-year Treasury note. The 10-year note traded at 2.62 percent Wednesday, up sharply from 2.54 percent a week earlier. It was trading at 2.63 percent Thursday morning. Bond yields rise when bond prices fall.