Sheriff Ed Gonzalez tweeted Thursday evening that 56-year-old Raul Rivas had paused briefly after coming across water on the roadway in northeast Harris County.
The man decided to chance it, and as he accelerated, his van became submerged in water, Gonzalez said.
Sheriff Ed Gonzalez speaks on fatality from Imelda
Rivas was taken to a hospital in critical condition, where he was pronounced dead.
Deputies said they are not sure whether he was the only person in the van.
In Jefferson County, a 19-year-old was attempting to move a horse when they were electrocuted and drowned, according to family members.
Now, the death toll has risen to at least five.