Via National Weather Service: Preliminary data from at least one Texas rain gauge appears to have broken the Texas tropical cyclone rainfall record and a new contiguous United States tropical cyclone rainfall record may have also been established. Cedar Bayou, near Mont Belvieu, Texas, recorded a preliminary rainfall associated with Tropical Storm Harvey of 51.88 inches as of 3:29 pm CDT (rainfall accumulation since 7 am CDT, Friday, Aug. 25, 2017). This reading is higher than the previous record for Texas of 48 inches during tropical cyclone Amelia of 1978 in Medina, Texas.
The all-time United States tropical cyclone rainfall record of at least 52 inches occurred during tropical cyclone Hiki in Kauai, Hawaii in 1950. It is certainly still possible rainfall from Tropical Storm Harvey may exceed the all-time United States record but no official rain gauge has reported a value in excess of 52 inches as of 5 pm EDT. (link)