* WHAT...For the first Extreme Heat Warning, dangerously hot conditions with heat index values up to 111 expected. For the second Extreme Heat Warning, dangerously hot conditions with heat index values up to 113 expected. * WHERE...Portions of northwest and west central Arkansas and east central, northeast, and southeast Oklahoma. * WHEN...For the first Extreme Heat Warning, until 8 PM CDT this evening. For the second Extreme Heat Warning, from noon to 8 PM CDT Tuesday. * IMPACTS...Heat related illnesses increase significantly during extreme heat and high humidity events.