The National Weather Service forecasts a multi-day heat wave for late June 2026 affecting the lower Great Lakes, mid-Atlantic, Mississippi and Ohio River valleys, Great Plains, and Southeast, with daytime highs in the 90s to low 100s Fahrenheit and heat indices up to 115 F. Cities including New York, Philadelphia, Baltimore, Chicago, St. Louis, Detroit, Dallas, and Memphis are projected to experience sustained high temperatures and overnight lows in the 70s. Two sources provide the information, with one bias perspective represented.