Wildfires, storms and record-breaking heat: Extreme weather advisories cover big swath of U.S.

Wildfires in California, thunderstorms and threats of flash flooding in the Midwest and extreme heat in the Northeast: A wide range of severe weather events are raging across the nation on Tuesday, putting millions of Americans under weather advisories.

Near Southern California, evacuation orders and warnings remained in effect Tuesday as wildfires raged near Burro Peak and across the Simi Valley region.

The Sandy Fire in Simi Valley, located about 30 miles northwest of Los Angeles, raged across nearly 1,400 acres since it began Monday morning. Only 5% of the fire had been contained as of 8:30 a.m. local time on Tuesday, according to the California Department of Forestry and Fire Protection.

People living in more than 10,000 homes in that region were ordered to evacuate Monday.

Firefighters are working toward full containment and public safety personnel are coordinating efforts to repopulate evacuated areas throughout the day as the fires are contained, according to the Ventura County Fire Department, the main agency responding to the fire.

Air quality alerts remained in place for the Los Angeles region on Tuesday due to the smoke from the Sandy Fire.

In the Midwest, parts of Missouri and Illinois experienced widespread showers and thunderstorms Tuesday morning, with some of that rainfall leading to flash flooding in some areas.

Flood watches are in effect for an estimated 7 million people, including residents of Kansas City and St. Louis, Tuesday. In the afternoon, these areas may be facing severe thunderstorms, damaging wind gusts and even large hail, according to the National Weather Service.

More than 53 million people are under severe storm threats from southwestern Texas to northern Vermont. More than 300 storm reports — including wind, hail and tornadoes — were reported across the nation in the last 24 hours. On Tuesday, damaging winds are possible across the entire region with a small chance of isolated tornadoes.

Meanwhile, residents in the Northeast and New England are grappling with the effects of a record-breaking heat wave. Heat advisories are in effect, affecting 32 million people in the region that includes cities like Philadelphia, Boston and New York.

This is only the second time in history that a heat advisory has been issued for New York City during the month of May.

In cities including Albany, Hartford, Boston, Buffalo, Washington, D.C., Philadelphia and Raleigh, soaring temperatures into the upper 80s and low 90s are expected to set temperature records.

A combination of high temperatures and humidity in the area is expected to make it feel like it is between 95 and 99 degrees.

In Newark, New Jersey, Mayor Ras J. Baraka activated the first Code Red alert of the year. The hot weather health warning advises residents to take precautions to prevent serious illness from extreme heat, as the heat index in the city is expected to reach 97 degrees on Tuesday.

NBC News Top Stories wp:paragraph