...RED FLAG WARNING NOW IN EFFECT FROM 11 AM TO 9 PM CDT TUESDAY FOR WIND AND LOW RELATIVE HUMIDITY FOR SOUTH CENTRAL SOUTH DAKOTA... * AFFECTED AREA...In South Dakota, Hughes and Lyman. * WINDS...Northwest 20 to 30 mph with gusts up to 40 mph. * RELATIVE HUMIDITY...As low as 20 percent. * IMPACTS...Any fires that ignite will spread rapidly and become difficult to control or suppress.