Forecast: The East Coast’s First Summer Heat Wave Is on Its Way

Prepare to sweat on the East Coast through next week. The first heat wave of the summer is coming.

The weather pattern is shifting, and a heat dome will traverse from the West to the Eastern United States, baking most of the eastern half of the country, including major cities from Chicago to New York, in stifling temperatures for days.

What makes this noteworthy and potentially dangerous is the timing. The first heat wave of the season can come as a shock to the human body, which hasn’t entirely adapted to summer swelter.

New Yorkers, for example, have had a moderately light season thus far, with temperatures not yet reaching a Popsicle-melting 90 degrees. Central Park typically hits 90 for the first time in the first week of June.

These temperatures are abnormal for June

As far as summer heat waves go, this isn’t necessarily extreme. According to Bryan Jackson, a meteorologist with the Weather Prediction Center in College Park, Md., it is more likely to be a “typical summer heat wave and is “not an event to overhype.”

The pattern and location of this heat wave looks remarkably similar to that of a heat wave that struck in June 1994, forecasters said Friday.

That summer reporters from The New York Times said that the heat “was like a blast from an open oven door” and that “emergency rooms reported an increase in back injuries to people who strained to install air-conditioners quickly.”

What concerns Mr. Jackson and other forecasters is that, as with the 1994 heat wave, temperatures are expected to be abnormally high for June, and the heat could persist for days and in some areas through the entire week.

The duration is of particular concern: The more days in a row of persistent record hot temperatures, the more impact heat has on the body.

The heat begins earlier in the Midwest and South

The forecast shows that this heat wave may likely last beyond Friday and could begin as early as Sunday in the Midwest and Tuesday in the Northeast.

In the South, people in places like Atlanta will have a precursor heat event this weekend, with the actual temperature rising to nearly 100 on Saturday.

But the air is expected to be drier than what people from Atlanta are commonly used to, and in the proceeding days, the temperature might drop, but the humidity will be on the rise, making it feel as hot or hotter than it was on Saturday.

The moisture will also spread across the Midwest and into the Northeast as the temperatures rise, often making it feel much hotter than the actual temperature and reducing the amount the temperature will cool off to at night.

The heat dome may allow for warmer temperatures than forecast

Most areas will likely reach a heat index in the 90s to low 100s, and people should take extreme caution, meaning there is some risk of heat stroke, heat cramps or heat exhaustion after long exposure or exercise outdoors. Some locations may even reach a heat index with dangerous or extremely dangerous thresholds.

There is always a worry that the temperatures and heat index will climb to temperatures higher than advertised, Mr. Jackson said.

The heat dome phenomenon, like what will occur next week, allows for a layer of the atmosphere to act like a clear lid that lets warm air in but won’t let it escape. This pattern allows for at least some probability that temperatures could reach 100 degrees in some locations, pushing above the current forecast and creating more dangerous conditions.

The warmest days in the Northeast are expected to be Tuesday through Thursday, and the best place to cool off might be by the seashore or lakeshore, where the beach breezes may help regulate the heat.