EL PASO, Texas — The nation began readying for an arctic storm that could plunge temperatures around the country, but on the southern border many migrants say they didn't know they were in for colder, nastier weather. Grisleida, who migrated from Venezuela and declined to give her last name, waited on the sidewalk with her young children, ages 8 and 6, near the Greyhound station. She crossed the border Monday with her husband, but he has been deported to Mexico. She has been sleeping at a shelter where she tries to arrive early each evening to get a spot inside....