WASHINGTON — A fourth straight monthly increase in sales of existing homes provided the latest evidence Thursday that the U.S. housing market is rebounding from a weak start to the year.

Housing has been a drag on an otherwise strengthening economy, in part because a harsh winter delayed many sales. But Americans are stepping up purchases as more homes have been put up for sale. And low mortgage rates and price gains have made homes more affordable.

“The momentum is in the right direction,” said Andrew Labelle, an economist at TD Bank. “Sustained jobs gains, as well as the fall in mortgage rates since the beginning of the year, appear to have unleashed at least some pent-up demand.”

Sales of existing homes rose 2.4 percent in July to a seasonally adjusted annual rate of 5.15 million, the National Association of Realtors said Thursday. That was the highest annual rate since September of last year.

The increase follows other encouraging signs that the housing market is improving. The pace of home construction starts surged 15.7 percent in July to a seasonally adjusted rate of 1.1 million homes, the government said. Applications for building permits, a gauge of future activity, also strengthened last month.

And a survey of homebuilders released Monday showed they were more confident about future sales.

The encouraging readings contrast with reports earlier this year, when weak sales and limited building led economists to characterize housing as a faltering piece of the economic recovery.