Excessive Heat Warnings remain in effect across the Mississippi and Ohio River Valleys as heat indices on Thursday climb into the 105 to 115-degree range.   

Heat Advisories are also in effect along the I-95 corridor from Philadelphia to Connecticut, while Excessive Heat Warnings are posted for the desert Southwest.  

Forecast heat index temperatures for Thursday. 

Forecast heat index temperatures for Thursday.  (Fox News)

Scattered, severe storms will move from the High Plains into the Northern Plains and eventually portions of the Midwest.   

Large hail, damaging winds, heavy rainfall and isolated tornadoes will be possible.  

The severe weather threat for Thursday.

The severe weather threat for Thursday. (Fox News)

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One disturbance in the Caribbean will have the chance to form into a tropical depression or storm as it moves near the Yucatán Peninsula this weekend, then into the western Gulf on Sunda or Monday. Texas and Louisiana will have to monitor this one.   

Current tropical weather activity.

Current tropical weather activity. (Fox News)

Another disturbance southeast of Bermuda will likely develop, but remain east of Bermuda in open ocean.