Extreme weather was threatening to upend July 4 holiday travel plans, with severe thunderstorms and heavy rains set to hit the Plains and Eastern states and searing heat affecting the U.S. Southeast, Southwest and Pacific Northwest.
The big picture: Tens of millions of people were under severe thunderstorm watches or affected by heat warnings and advisories Monday, as Grand Canyon National Park officials said a woman died while hiking in temperatures "well over 100°F" near Tuweep, Arizona. Excessive heat warnings were in place for the canyon and across the Southwest.
Torrential rains flooded Chicago's streets and forced NASCAR officials to postpone a race through the city, as the National Weather Service issued hazardous weather alerts for over 110 million Americans during the extended July Fourth holiday weekend.
State of play: Chicago train services were suspended, buses were temporarily rerouted and Illinois State Police said parts of Interstate highways 55 and 290 were shut due to flooding, per WLS-TV.
California officials and wildlife experts are urging beachgoers over the extended Fourth of July holiday weekend to be alert to sick sea lions displaying unusually aggressive behavior towards people.
Driving the news: Channel Islands Marine & Wildlife Institute (CIMWI) executive director Sam Dover told Axios seven sea lions that had fallen ill to neurotoxins from offshore algae blooms had bitten three beachgoers, two surfers, one paddle boarder and a diver as of Saturday.
