Strong-to-severe thunderstorms are expected to pop up from the Midwest down into the Plains and across the mid-Atlantic.
HIGHWAYS CLOSED, OIL REFINERY THREATENED AS GREEK WILDFIRES RAGE ON
The threat of severe storms on Wednesday from the Midwest to the Mid-Atlantic (Credit: Fox News)
Some of these storms will contain large hail, damaging winds and isolated tornadoes, along with heavy rain that could lead to flash flooding.
Rain forecast through Friday night in the Midwest, Plains (Credit: Fox News)
This comes as dangerous heat bakes the Southern Tier of the country, with tens of millions of people under heat alerts once again on Wednesday.
Heat alerts through Saturday night in the southern U.S. (Credit: Fox News)
In addition, smoke from the Canadian wildfires is causing poor air quality over sections of the Great Lakes and Northeast.
Meanwhile, Tropical Storm Calvin will move south of Hawaii.
The forecast track for Tropical Storm Calvin near Hawaii (Credit: Fox News)
Rain forecast for Hawaii through Thursday morning (Credit: Fox News)
However, heavy rain and tropical-storm-force winds will still be felt, especially for the Big Island.