* AFFECTED AREA...In South Dakota, Campbell, McPherson, Walworth, Edmunds, Potter, Faulk, Sully, Hughes, Hyde, Hand and Buffalo. * WINDS...South 20 to 30 mph with gusts up to 40 mph. * RELATIVE HUMIDITY...As low as 27 percent. * IMPACTS...Any fires that ignite will spread rapidly and become difficult to control or suppress.