A sprawling heat dome is set to bring days of dangerous heat and oppressive humidity across much of the central and eastern United States, with more than two dozen states expected to face potentially hazardous conditions through the Independence Day weekend.
The heat will build over the central U.S. before expanding into parts of the East, pushing temperatures into the 90s across a wide area and sending some major cities close to or above 100 degrees Fahrenheit.
AccuWeather forecasters warn that high humidity will make the heat feel even more intense, with AccuWeather RealFeel® Temperatures expected to climb above 100 degrees in many locations and possibly exceed 110 during the hottest part of the day.
Heat Dome to Expand From Midwest to East
The developing heat dome will strengthen over the central United States and grow in size through the week. The Mississippi and Ohio valleys are expected to endure widespread highs in the 90s, along with uncomfortable humidity.
Chicago is forecast to reach 90 degrees or higher for four to five consecutive days. St. Louis could see at least eight straight days in the 90s, with highs approaching 100 degrees.
Those temperatures are well above typical late June and early July averages. Normal highs this time of year are generally in the mid-80s in Chicago and the upper 80s in St. Louis.
AccuWeather meteorologists said dew points will climb well into the 70s in many areas, creating a thick, muggy air mass that will make conditions feel especially uncomfortable.
Major Cities Face Strong and Severe Heat Waves
The AccuWeather HeatWave Counter and Severity Index™ shows several major cities facing notable stretches of dangerous heat around the Fourth of July holiday.
New York City is expected to experience a moderate heat wave from July 1 through July 3. Philadelphia could face a strong heat wave from June 30 through July 5, reflecting both the duration and intensity of the heat.
Chicago is also forecast to endure a strong heat wave from June 29 through July 3.
Farther south, Raleigh, North Carolina, may experience one of the most intense heat waves among the highlighted cities. From June 30 through July 4, temperatures are forecast to exceed the city’s higher 95-degree threshold for several consecutive days, pushing the event into the severe category.
Some Cities Could Reach 100 Degrees
The worst of the heat and humidity will spread into the Eastern states by midweek and could linger into the Fourth of July holiday in some areas.
Philadelphia is forecast to reach 100 degrees on two or three days, despite average highs normally being in the upper 80s. Washington, D.C., could see highs at or above 100 for as many as four days in the week ahead.
New York City may also approach or reach 100 degrees for a couple of days during the middle to latter part of the week. Nearby Newark, New Jersey, has an even higher chance of reaching or exceeding 100 degrees on at least two days.
Even in areas where actual air temperatures stay in the lower 90s, RealFeel® Temperatures could make conditions feel far more dangerous.
Hot Nights Could Increase Health Risks
Forecasters warn that some of the most concerning heat may occur at night.
While a handful of locations may set daily record highs, many more could challenge or break records for overnight warmth. In some larger cities, temperatures may not drop below 80 degrees during the peak of the heat wave.
That lack of nighttime cooling can increase health risks, especially for people without access to air conditioning.
Urban areas are particularly vulnerable because pavement, concrete and brick absorb heat during the day and release it slowly overnight. Long daylight hours in late June and early July can make this urban heat island effect even stronger.
Humidity Will Make It Harder for the Body to Cool Down
High humidity will play a major role in the danger of this heat wave. When dew points climb into the 70s, sweat evaporates more slowly from the skin, making it harder for the body to cool itself.
Prolonged exposure to heat and humidity can lead to heat exhaustion and heatstroke.
Young children, older adults, outdoor workers, people with respiratory conditions and those without reliable cooling are among the most at risk.
Health experts recommend drinking plenty of water, avoiding strenuous outdoor activity during the hottest parts of the day, checking on vulnerable neighbors and relatives, and spending time in air-conditioned buildings or cooling centers when possible.
Pets Also Face Heat Dangers
Pet owners are also being urged to take precautions.
Animals should be brought indoors during the hottest parts of the day and given access to fresh water. Walking dogs on hot pavement during daytime hours should be avoided, as pavement can quickly become hot enough to burn paws.
Heatstroke and dehydration can affect pets quickly, especially during long stretches of extreme heat.
Air Quality Could Worsen
Heat, humidity and light winds may also contribute to poor air quality in parts of the affected region.
Wildfire smoke from the western United States could drift eastward during the week. While the smoke may slightly reduce sunshine and keep daytime highs a few degrees lower in some places, it could worsen air quality if it mixes down to the surface.
People with asthma, heart disease or other respiratory conditions may need to limit outdoor exposure if air quality declines.
Storms May Bring Temporary Relief
Along the edges of the heat dome, complexes of thunderstorms are expected to develop and move from the Rockies across the northern Plains and into parts of the Midwest and Northeast.
Additional storms may also form along the Gulf Coast.
These storms could briefly lower temperatures in some areas during the afternoon, but they may also bring localized severe weather.
By the Independence Day weekend, a shift in the jet stream is expected to push the heat dome back toward the Plains. That change should allow cooler air and more frequent thunderstorms to move into parts of the East.
Boston may begin to cool down before July 4, while Washington, D.C., may not see meaningful relief until late on Independence Day or Sunday.
Dangerous Heat Ahead of the Holiday Weekend
With millions of people expected to spend time outdoors ahead of the Fourth of July, forecasters are urging residents to take the heat seriously.
The combination of high temperatures, oppressive humidity, hot nights and potential air quality issues could make this one of the more dangerous weather events of the early summer season.
Until relief arrives, the safest options will be air conditioning, cooling centers, shaded areas, pools, beaches and cool showers.
For many communities from the Midwest to the East, the days leading up to Independence Day will not just feel hot — they could become dangerous.
News compilation from: accuweather
