Weslaco ( ) is a city in Hidalgo County, Texas, United States. As of the 2020 census the population was 41,103, Studies from 2023 show the population is 43,053 and in 2020 the estimated population was 40,160. It is at the southern tip of Texas in the Rio Grande Valley near the Mexican border, across the Rio Grande from the city of Nuevo Progreso, Rio Bravo, Tamaulipas.