More Americans signed contracts to buy homes in March, the third straight month of gains as housing heats up with the start of the spring buying season.

The National Association of Realtors says its seasonally adjusted pending home sales index rose 1.1 percent to 108.6 last month. The index has climbed 11.1 percent over the past 12 months after having dipped in 2014.

Pending sales improved in the South and West. But the number of signed contracts fell in the Northeast and Midwest, two areas that many economists expected to show rebounds after a harsh winter hurt sales at the start of 2015.

Pending sales are a barometer of future purchases. A one- to two-month lag usually exists between a contract and a completed sale.