The Northeast is preparing for heavy rainfall that could lead to flash flooding, following a period of extreme heat. The National Weather Service has issued warnings for several major cities, including Philadelphia and New York City, as storms are expected to bring 2 to 4 inches of rain, with localized amounts potentially reaching 8 inches in some areas.

AccuWeather meteorologists have cautioned that flash flooding can occur rapidly, especially in regions with hilly terrain and poor drainage. Chief Meteorologist Jonathan Porter emphasized the dangers of driving through flooded roads, stating, "It’s impossible to know how deep the water is, how fast it is moving or if the road or bridge underneath has been compromised or washed out. Most flash flooding fatalities involve vehicles and are preventable."

The heavy rain is forecast to begin Thursday and continue into Friday, with thunderstorms also possible. The I-95 corridor is expected to be particularly affected, leading to potential travel disruptions during peak commuting hours. Major airports may also experience delays due to reduced visibility.

In addition to the rain, a significant heat wave continues to impact over 50 million Americans across 11 states, with extreme heat warnings in effect for the lower Mississippi River Valley. Heat indices in these areas could reach between 110 and 120 degrees.

As the storms move through, a cooler and less humid air mass is expected to follow, providing relief from the oppressive heat. This change in weather is anticipated to bring temperatures down to the 60s in some areas along the I-95 corridor, with mountain regions possibly dipping into the 30s.

The Pacific Northwest is also facing challenges, with red flag warnings issued due to strong thunderstorms that could ignite new wildfires. In Utah, low humidity levels combined with high winds are raising concerns about fire conditions. The Dragon Bravo Fire near the Grand Canyon has already burned over 94,000 acres, with containment efforts struggling.

Meanwhile, air quality alerts are in effect for Minnesota, Wisconsin, and Michigan due to smoke from 579 wildfires burning in Canada, with 255 of those fires currently classified as out of control. Residents in affected areas are urged to stay alert for flash flood warnings and take necessary precautions.