The new area code for Austin, 737, went into effect about a year ago. Starting on July 1st, there will be a new area code for the Houston area.
The area code 346 will join 713, 281, and 832 to cover the counties of Harris, Fort Bend, Waller, Austin, Montgomery, San Jacinto, Liberty, Chambers, Galveston and Brazoria.
Currently Houston is the city in Texas with the most area codes. Dallas is in second place with three area codes: 214, 972, and 469. However, if you include Fort Worth, and hyphenate the cities, then Dallas-Fort Worth would win with a total of five. The area codes 817 and 682 currently cover the Fort Worth area.