A mixed bag of severe weather and dangerously hot temperatures was expected for parts of the United States on Independence Day, after Tropical Storm Colin doused the Carolinas over the weekend.

Parts of the Pacific Northwest, Northern Plains, the Upper Midwest, Great Lakes and Northeast were expected to face heavy rainfall through Monday night, the National Weather Service said.

Montana was under a heightened threat of severe thunderstorms, including lightning and hail the size of golf balls, the weather service in Billings said.

Along the West Coast, a cold front was expected to continue through the middle of the week. Dry conditions, coupled with low humidity and strong winds, would elevate the risk of wildfires. Wind gusts could reach up to 45 mph in western Utah, the weather service in Salt Lake City said.

By early Monday, more than 5 million people in Arizona, Nevada and Utah were under red flag warnings, indicating increased fire danger. There were two active fires in Nevada, encompassing more than 2,000 acres. Dangerous fire weather was also predicted for a large swath of Alaska.

As families gather for cookouts and fireworks, high temperatures were expected in parts of the country. Nearly 30 million people in the Midwest and Central Plains were under a heat advisory Monday, the weather service said. Portions of Kansas and Missouri could see heat index values climb to 107 degrees. Similar sweltering conditions were also forecast for parts of Arkansas, Kentucky and Nebraska. Hot weather in some locations was expected to continue through at least Wednesday.

“If attending outdoor activities on Independence Day, drink plenty of water and take frequent breaks in the shade or an air-conditioned building,” the weather service said.

Meteorologists in Kansas City also advised that, as temperatures rise, people should limit their consumption of alcohol and caffeine and wear light-colored, loose clothing.