Extreme heat alerts issued for central, eastern U.S. as heat dome builds June 20 onwards

A large heat dome is forecast to settle over the central and eastern United States beginning June 20, raising daily and nighttime temperatures across a broad area and consequently inducing the season’s first heat wave. Around 220 million people are expected to experience daytime highs above 32°C (90°F), with over 35 million exposed to temperatures exceeding 38°C (100°F).

Heat dome is a semi-stationary high-pressure system that traps warm air and inhibits overnight cooling, with nighttime lows staying in the range of 24–27°C (75–80°F).

The National Weather Service (NWS) has issued major to extreme risk alerts (Level 3–4) for much of the Midwest and parts of the Great Plains, with additional alerts likely for the Northeast, including major urban centers such as New York City, Philadelphia, and Washington, D.C.

Peak impact zones include eastern Colorado, Kansas, Nebraska, Missouri, Iowa, Illinois, Indiana, Ohio, and stretching into Pennsylvania, New Jersey, and parts of New England.

These areas will feel especially hot and uncomfortable, with the heat index reaching dangerous levels due to high humidity and dew points in the mid-20s °C (70s °F). Overnight temperatures are also expected to stay warm, usually between 24 °C and 27 °C (75–80 °F), which means little relief from the heat at night.

In the aforementioned areas, temperatures are forecast to exceed 38–40°C (100–104°F). This extended heatwave is especially concerning because the constant high temperatures increase the risk of heat exhaustion and heatstroke. People most at risk include older adults, young children, outdoor workers, and anyone without access to air conditioning.

Localized convective thunderstorms and possible severe weather are also expected along the periphery of the heat dome, from the southern Plains to the interior Northeast. This includes areas from New Mexico and Texas through the central Plains and into the interior Northeast. These may produce heavy rainfall capable of triggering localized flash flooding in the worst-case scenario.

The ongoing conditions align with the June outlook by the National Oceanic and Atmospheric Administration (NOAA), which predicted above-average temperatures for most of the contiguous United States throughout summer 2025.

Citizens are advised to remain hydrated, avoid prolonged outdoor exposure during peak heat hours, and seek air-conditioned environments when possible.