The route travels to the southeast, passing a section of the Lower Rio Grande Valley National Wildlife Refuge, before turning to a more easterly path and crossing into Willacy County. SH 186 runs along Hidalgo Avenue in Raymondville, where it crosses  I-69E / US 77.
The route traverses southeast, encompassing a section of the Lower Rio Grande Valley National Wildlife Refuge, then turns eastwards to enter Willacy County. SH 186 runs along Hidalgo Avenue in Raymondville, where it intersects with I-69E/US 77.