Texas' governor sent National Guard troops to Houston Monday as torrential rainfall flooded homes and highways in southeastern Texas and parts of Louisiana, where more than 100 patients had to be evacuated from a nursing home.

Houston Mayor Bill White toured his city by helicopter and described seeing "block after block after block flooded."

As much as 10.5 inches of rain was reported in the Houston area by the height of the morning rush hour, said Rusty Cornelius, administrative coordinator for Harris County Emergency Management. Almost 6 inches of rain fell in just 75 minutes near Hobby Airport, the National Weather Service reported.

Gov. Rick Perry ordered the Texas Army National Guard to send trucks, helicopters, swift water rescue teams and an incident management team to the flooded area.

No deaths had been reported, but roads across the Houston area, including Interstate 10 and other major arteries, were flooded and vehicles were stalled. Hobby Airport was closed for more than 2 hours because employees couldn't get through the flooded roadways to work.

The storm cell that swamped the city was moving out by midday, but more rain was expected by evening. A flood watch was in effect until Tuesday morning for about a dozen counties in southeastern Texas.

"We probably have another 48 hours of this," said Josh Lichter, a National Weather Service meteorologist in Houston.

In Louisiana, emergency crews evacuated more than 100 patients from Holly Hill Nursing Home, where water was 8 inches deep in some of the halls. Fire departments from Sulfur and Lake Charles and two ambulance companies moved patients to another nursing home in Lake Charles, about 15 miles away, officials said.

Some houses in Sulphur, La., were flooded, and residents were urged to stay home, Assistant Police Chief Glenn Berry said. The same area was battered by Hurricane Rita last September.

"There's pretty widespread flooding around the parish. A lot of roads are closed," said Dick Gremillion, the Calcasieu Parish, La., emergency preparedness director.

In Houston, a YMCA building was surrounded by water and people were standing on the roof Monday morning as water in the parking lot inched up on the vehicles' doors. Emergency crews answered about 500 calls for help, mostly from stranded motorists, White said.

"We live in Houston, Texas, and you can't be surprised at flooding in Houston," White said. "When you have this much rain in a short period of time at a place that's near sea level, then you still have some real risk."