The crash happened just before 10 p.m. Tuesday in the 7500 block of Garth Road near Seabird Street.
Investigators said the woman and her husband were crossing the road, heading to a store, when the woman was hit by an oncoming Chevy pickup truck.
Deputies said the driver of the pickup truck had just changed lanes to avoid another driver who slowed down rapidly when he struck the pedestrian.
The woman was pronounced dead at the scene.
Due to the circumstances of the crash, Harris County sheriff's deputies are calling it a "tragic accident."
"As he was changing lanes, it's very foggy out here. [The driver] never saw the pedestrian. [He] just knew that he struck something," Dashana Cheek with HCSO said. "[He] stopped, and in fact, had struck the female. The female did die from injuries here on the scene."
Deputies said the couple was not walking in the crosswalk.
HCSO investigators said the driver stayed at the scene and did not show any signs of impairment.
The victim's husband was not injured in the crash.