Record-threatening heat wave to expand across the U.S.

• Based on NWS forecasts, 241 million Americans are likely to see temperatures at or above 90°F during the next 7 days.

Context: Climate change greatly increases the likelihood of heat waves, as well as their intensity and duration.

The big picture: A large area of high pressure, also known as a heat dome, will build over much of the central and eastern half of the country into next week, computer models and NWS forecasts show.

• Highs are forecast to be well into the 90s, with some temperatures in the low 100s in the South and potentially Mid-Atlantic, especially between June 17-20, with overnight lows only dipping into the upper 70s.
• The NWS forecast for June 18, for example, shows nearly every location with temperatures in the 90s from Chicago to Boston, south to Florida and also across the Central states.

• This heat could threaten records, and possibly yield the first 100°F day in Washington, D.C., since 2016.

What's next: The Climate Prediction Center is predicting the heat threat is likely to continue across the East through the end of June, and build once again in the West and Southwest.

Threat level: The latest computer model projections for the summer overall show a robust signal for unusual heat and dry conditions across the Southwest in particular, with an overall tilt toward hotter-than-average conditions across the country.