I was in San Antonio in October 1998 - when 26 inches fell in one day just north of town. A tropical storm was stuck of the west coast of Mexico, and a front pumped all that moisture up to New Branufels and surrounding towns. Some kind of flooding.
I remember that storm. Those storms also affected Houston. Up to 16 inches fell. The moisture were fed from two Pacific Hurricanes, Lester, and Madeline. In October 1994, we had a really bad rainstorm, where some areas got over 20 inches in one day. It was caused by remnant of Hurricane Rosa and slow moving cold front. In 2001, Tropical Storm Allison dumped 28 inches in 12 hours. 40 inches fell in five days.