Heat dome brings extreme temps and humidity to the East, prompting early school dismissals NBC NewsIowa school closings: Iowa districts closing early due to sweltering heat KCCI Des MoinesTriple-digit heat strikes again: Late summer heat to scorch millions USA TODAYHeat wave roasts more than 50 million from Ohio Valley to Washington D.C. AxiosTens of millions bake under extreme heat in eastern United States Yahoo! Voices