OMAHA, Neb. (AP) — Frigid weather that has sent temperatures plunging across Middle America also had power and gas utilities urging customers to dial down the thermostat.

Utility companies serving Nebraska, Iowa, Kansas and Missouri issued pleas Sunday and Monday for customers to conserve power as temperatures plummeted and demand for energy soared across the Plains.

"Much as it does in summer, high demand can put additional strain on our system," a message from Omaha Public Power District to customers read. "We are seeing similar effects now, only this time with record cold instead of heat."...