SAN ANTONIO — The San Antonio and Austin real estate markets are on fire.

However, low housing inventories in both cities means housing is in high demand.

Last month, 1,300 homes were sold in Austin, a 6 percent increase year-to-year. San Antonio saw a giant 17 percent spike year-to-year, selling 2,800 homes in April.

Real estate experts say builders are having a hard time keeping up with buyers.

Right now, if new construction came to a stop, buyers in both booming markets would buy every available home for sale in both cities in less than three months.

"You're seeing a boom in new construction sales, and these builders cannot build them fast enough,” said Sara Gerrish with the San Antonio Board of Realtors. “I mean, they are going under contract almost immediately it seems like in these subdivisions."

The average home price in San Antonio is a little more than $250,000. In Austin, depending on what part of town you're looking to buy in, the average is well above $300,000.