Boston metro area home prices crept up about 2 percent in May, as prices nationwide climbed for the fourth consecutive month, a closely watched survey showed on Tuesday.

U.S. single-family home prices rose for the fourth month in a row in May on a seasonally adjusted basis, suggesting the recovery in the housing market continued to gain traction.

The S&P/Case-Shiller composite index of 20 metropolitan areas gained 0.9 percent in May on a seasonally adjusted basis, topping economists’ expectations for a 0.5 percent gain.

On a non-seasonally adjusted basis, prices fared even better, jumping 2.2 percent.

Boston, along with Charlotte, N.C., and Detroit, Mich., saw their annual rates of return deteriorate compared to April, even though prices rose during the month, the report said.

Boston scored a 150.67 on the price index, a 2.4 percent increase over the previous month and a 0.1 increase over the year.

"With May’s data, we saw a continuing trend of rising home prices for the spring," David Blitzer, chairman of the index committee at Standard & Poor’s, said in a statement.

Still, Blitzer cautioned that spring and summer are traditionally strong buying months and that gains need to continue into the rest of the year.

"The housing market seems to be stabilizing, but we are definitely in a wait-and-see mode for the next few months."

The rate of decline on a yearly basis moderated, with prices down 0.7 percent compared to a 1.9 percent drop in April.