WASHINGTON — Fewer people signed contracts to buy homes in August, the fifth decline in the past six months. The 2.6 percent drop continues to reflect the worsening shortage nationwide of homes being listed for sale.

The National Association of Realtors said that its pending home sales index fell to 106.3 in August from 109.1 in July. It’s the index’s lowest point since a 106.1 reading in January 2016 and was 2.6 percent lower than a year ago.

Pending sales contracts are a barometer of future purchases. Sales are typically completed a month or two after a contract is signed.

The Realtors said hurricanes Harvey and Irma had a particularly negative impact in the South, where pending sales contracts declined 7.8 percent. Pending sales fell 3.1 percent in the Northeast, but ticked up slightly in the Midwest and West.

Homebuyers are caught in a period of rising home values, a limited selection of properties on the market and a shortage of savings.

A new survey released Wednesday by the real estate firm Zillow found that only 39 percent of millennial buyers this year are able to make the recommended 20 percent down payment – and those that do are more likely to rely on money from family and friends. Older buyers often already own homes and can afford a larger down payment.