It was pickup time at the day care. As other children and parents milled about, Tanya Leshchenko sat on a bench in a hallway and bundled her 5-year-old daughter into a purple winter coat. But before stepping outside, one more task remained.

Ms. Leshchenko checked an online chat group for warnings of incoming attack drones. The group posts crowdsourced alerts in the city of Kherson, in southern Ukraine, where the daily risk of death from flying robots offers a vision of an eerie, postapocalyptic future.

One warning last fall simply said, “I hear a drone!” — an ominous buzzing that has become a grim, intermittent soundtrack in the city. On the day when Ms. Leshchenko, 36, was picking up her daughter, however, the sky was calm. They walked out and headed toward the bus stop.

“You cannot outrun a drone,” Ms. Leshchenko said, before adding: “It’s scary.”

In Kherson, a city of broad tree-lined boulevards and stately czarist-era mansions, residents fear the open sky. The entire city lies within range of cheap Russian quadcopter drones, which Moscow’s forces launch from territory they occupy just across the Dnipro River.