Mortgage rates surged again this past week, completing a consistently steep ascent in May, according to data released Thursday by Freddie Mac.

The 30-year fixed-rate average jumped to 3.81 percent with an average 0.8 point, its highest mark in the past year. May began with the 30-year hovering at 3.35 percent, well below last year’s reading at the start of the month; however, four straight weeks of increases have pushed the average above last year’s reading of 3.75 percent.

The 15-year fixed rate average followed suit, rising to 2.98 percent from 2.77 percent last week, with an average 0.7 point. One year ago, the average was 2.97 percent.

Hybrid adjustable rate mortgages, on the other hand, remained below their averages from last May. The five-year ARM rose slightly to 2.66 percent, down year-over-year from 2.84 percent, and the one-year dropped slightly to 2.54 percent, down from 2.75 percent a year ago.

A Freddie Mac executive pegged the rising fixed-rate averages to some recent signs of economic improvement, including higher home prices and improving consumer confidence.

“Fixed mortgage rates followed long-term government bond yields higher following a growing market sentiment that the Federal Reserve may lessen its accommodative policy stance,” Frank E. Nothaft, Freddie Mac vice president and chief economist, said in a statement, adding that the “improving economic data may have encouraged those views.”

Mortgage application volume slipped for the third consecutive week, according to the Market Composite Index generated by the Mortgage Bankers Association. The index dropped 8.8 percent, not quite as steep as last week’s 9.8 percent decline.

The MBA’s Refinance Index dropped 12 percent, marking the largest week-over-week tumble of the year, while the Purchase Index ticked up 3 percent.

The National Association of Realtors reported on Thursday that pending home sales improved marginally last month, rising 0.3 percent from March and 10.3 percent over April 2012. Contract signings are now at their highest level in three years.

“The housing market continues to squeak out gains from already very positive conditions,” Lawrence Yun, NAR’s chief economist, said in a statement. “Pending contracts so far this year easily correspond to higher closed home sales in 2013.”