Heat dome brings dangerous record heat across the U.S. through July 4

A heat dome locked in high pressure over large swaths of the United States, trapping humid air and raising the risk of heat illness during the July 4 travel period. The National Weather Service is forecasting dangerous to record-setting heat across the eastern two-thirds of the country, with heat indices reaching 100 to 110 degrees in parts of the central and eastern U.S.

The most hazardous conditions stretched from the Midwest to the East Coast, including Ohio, North Carolina and Washington, D.C., where high humidity made the heat more dangerous for older adults and people with respiratory problems. AccuWeather forecasts some cities could near 100 degrees and feel more than 110, while The Weather Channel forecasts record highs shifting eastward as a major heat wave builds across the Midwest and East during Fourth of July week.

NOAA’s Climate Prediction Center forecasts extreme heat continuing from week 1 into the July 4 holiday weekend across many areas of the central and eastern contiguous U.S., and its week 2 outlook shows the heat persisting into the following week. The outlook covers the Ohio Valley, North Jersey, Tennessee, Hampton Roads, Chicago and Minnesota, where high temperatures and humidity threaten to strain power demand, outdoor work schedules and holiday gatherings.

The CDC Heat and Health Tracker provides local heat and health information, including historic heat-related illness data. The National Weather Service’s HeatRisk tool helps identify people and places most sensitive to heat.

People should take steps to stay cool and safe once temperatures hit 85 degrees or the heat index reaches 90, a threshold that becomes easier to cross when dew points climb.

A July 4 records tool showed 2012 produced the most records among its 800 weather stations.