A man wearing a blond wig robbed the branch located on the 7800 block of Highway 11 around 1:40 p.m. Saturday.
The suspect entered the branch, walked up to a teller and said he had a gun as he demanded money. The teller complied and the suspect fled with an undisclosed amount of money.
He was described as a white man, between 40 and 50 years old, standing around 6 feet 2 inches with a medium build.
The suspect was sporting a handle-bar mustache, a white bandana over his head, a dark-hooded sweatshirt, blue jeans and gold mirror sunglasses.
The investigation is ongoing. Anyone with information was asked to contact Investigator Melissa Nieburger at the sheriff's Thermal station at (760) 863-8950.
CNS contributed to this report.