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Each weekday morning, OurAmazingPlanet takes the pulse of the Earth, reporting on natural phenomena and exploration news from around the globe.

Memphis Flooding: The Mississippi River has spilled over into downtown Memphis, where authorities are going door to door to ask people to leave. [Countdown: Mightiest Floods of the Mississippi River. ]

Flood Threat Moves South: The historic Mississippi River flooding has spread all the way to the Mississippi delta. [Related: What's Behind the Record Mississippi River Flooding? ]

EF-5 Number Three: The tornado that hit Hackleburg, Ala., has been rated an EF-5 on the tornado damage scale, the highest rating and the third EF-5 from last week's outbreak. [Related: The Tornado Damage Scale In Images ]

Many Still Missing: In Alabama, dozens of people remain missing after the historic tornado outbreak that struck one week ago.

Kentucky Derby Forecast: Rain and thunderstorms could make for a muddy race at Churchill Downs on Saturday. Could it be the coldest derby ever?

Previously on Our Daily Planet: Mississippi River Flooding and Throat of Fire Eruption Photos

Reach OurAmazingPlanet staff writer Brett Israel at Follow him on Twitter @btisrael.