Houston is fast gaining on the boroughs of Brooklyn and Queens, new population estimates from the U.S. Census show, as the Texas city grew at an estimated rate of 8.8% between 2000 and 2006.

With figures scheduled for release today, New York City is twice as big as any other municipality in the country, though cities in the South and Southwest are rapidly expanding.

Houston, with an approximate population of 2.1 million, is currently the fourth largest city in the country. If measured separately from New York City, Brooklyn and Queens would be the fourth and fifth largest cities, with populations of 2.5 million and 2.2 million, respectively.

Standing in contrast to many shrinking cities in the Northeast and northern Midwest, Fort Worth, Texas, and Raleigh, N.C., were estimated to have grown more than 20% between 2000 and 2006, as cities in warmer climates accounted for the vast majority of the fastest growing urban areas.

A notable Southern exception is New Orleans, which has lost an estimated 53% of its population since 2000.

The data show New York City as having grown 2.6% since 2000, with a population of more than 8.2 million people. Each year since 2003, the Bloomberg administration has challenged the estimates as too low.

A spokeswoman for the Department of City Planning said the city was reviewing this year’s data.