65 million Americans under heat alerts across the South

Some 65 million Americans are under heat alerts as a heat dome sits over parts of the South.

Heat alerts have been issued from Alabama up into Kansas City on Wednesday. Excessive heat warnings are in effect for major cities in Texas, Louisiana, Mississippi, Tennessee, Oklahoma and Kansas -- meaning several days of dangerous heat are expected. Across this region, the heat index -- what the temperature feels like -- is forecast to hit at least 110 degrees.

Record highs were seen in multiple cities across Texas and Louisiana on Tuesday, with more high temperatures expected to impact the region on Wednesday.

In Louisiana, Baton Rouge and Lake Charles saw record highs on Tuesday, with temperatures reaching 104 and 102 degrees, respectively. Record highs are possible again in Baton Rouge on Wednesday, where the high is forecast to reach 100 degrees.

In Texas on Tuesday, triple-digit temperatures tied for record highs in Dallas, Del Rio, State College and Victoria. Record highs are possible Wednesday in San Antonio and State College, with the highs forecast to reach 102 and 106 degrees, respectively.

It is forecast to feel like 110 to 115 degrees in Dallas; Austin, Texas; Little Rock, Arkansas; and New Orleans through at least Saturday.

The heat dome is then expected to move west into Arizona and California by the weekend and into next week.

An excessive heat warning has already been issued for Arizona -- including Phoenix. After a two-day break with temperatures below 110 for the first time in a month, the high is expected to be at 110 once again in Phoenix on Wednesday. Over the weekend, temperatures in the city are expected to reach nearly 115 degrees.

Residents in Arizona's capital have experienced weeks of temperatures at or above 110 degrees, with July its hottest month on record. Last week, the medical examiner's office in Arizona's Maricopa County was over capacity and had to bring in refrigeration units because of a spike in deaths in July amid a record-breaking heat wave, officials said.

Triple-digit heat is also expected to spread to Sacramento later this week. In Portland, Oregon, temperatures are forecast to reach the mid-90s.

Elsewhere, seven states -- from Utah to Kentucky -- are on flood alerts on Wednesday due to heavy rain. Some spots could see scattered storms that bring several inches of rain that could produce flooding.

St. Louis is forecast to be in the bull's-eye for heavy rainfall that could cause flash flooding. The additional rain comes after parts of Missouri saw more than half a foot of rain in eight hours on Tuesday, with roads and streets flooded.

Severe weather is also expected from Nebraska to Illinois on Wednesday and Thursday. Damaging winds and hail are likely to be the biggest threats, though an isolated tornado cannot be ruled out.