Warm temperatures again today are causing electric supply problems for Alliant Energy’s 461-thousand Iowa customers.Alliant spokeswoman Karmen Wilhelm says the heat is just one of the factors that’s caused a shortage of electricity for the company.She says the Duane Arnold nuclear power plant is down for a scheduled refueling, while two other plants have had unexpected outages that shut them down. The company has instituted its program that interrupts power to some homes and businesses during the day to save electricity. Wilhelm says 10 schools in Iowa, Illinois and Minnesota are involved in that plan. Iowa schools in Cedar Rapids, Marion and Anamosa had to let out classes early yesterday due to the power interruption.She says they’ve put the schools at the bottom of the interruption list so they can have enough power to finish the school day. Wilhelm says the problems should go away as the power plants are back up and running.Wilhelm says they’re asking customers to conserve as much electricity as they can until the normal power supply is flowing again.