* WHAT...For the Extreme Heat Warning, dangerously hot conditions with heat index values up to 105. For the Heat Advisory, heat index values near 100 expected. * WHERE...Southwest and south central North Dakota, including the James River Valley. * WHEN...For the Extreme Heat Warning, until 10 PM CDT /9 PM MDT/ this evening. For the Heat Advisory, from 10 PM CDT /9 PM MDT/ this evening to 10 PM CDT /9 PM MDT/ Thursday. * IMPACTS...Heat related illnesses increase significantly during extreme heat and high humidity events.