Regions of Tennessee

Memphis stands on the Chickasaw Bluffs at the top of the Delta, the only high ground the lower Mississippi offers for a hundred miles — which is why the city is there and why the flat country around it floods. It is the warmest corner of Tennessee and the one with the least terrain to slow a squall line down, and the 1811–12 New Madrid quakes that made Reelfoot Lake happened just upriver.

West Tennessee outside Memphis is river country twice over: the Mississippi on one side, the Tennessee on the other, and the Obion, Forked Deer and Hatchie draining the flat ground between them. It is the part of the state that floods first and dries last, and it sits far enough west that spring supercells arrive here before anywhere else in Tennessee.

This is the ground Dixie Alley crosses after dark. The Highland Rim and the southern basin take the tail end of the storm systems that come out of Mississippi and Alabama overnight, when they are hardest to warn for, and the same rim that makes the Duck and Elk rivers rise makes them rise fast.

The plateau is Tennessee's weather divide. It stands 1,000 feet above the basin, holds cold air and freezing rain long after Nashville has gone over to plain rain, and takes far more snow than anywhere else outside the mountains. It also drops storms down its western escarpment into the Caney Fork gorges, where an inch of rain turns into a wall of water.

Chattanooga sits in a bend of the Tennessee where the river cuts through Walden Ridge, and the terrain does the forecasting: the gorge channels wind, the ridges hold fog in the valley for days, and the Cumberland escarpment above Monteagle ices over while the city stays wet. April 27, 2011 put a violent tornado through the same corridor twice in one afternoon.

Knoxville sits in the Tennessee Valley with the Cumberlands on one side and the Smokies on the other, and 5,000 feet of relief inside an hour's drive. The valley traps cold air and fog; the crest above it takes more than 80 inches of rain a year, the wettest place in the eastern United States. The 2016 Gatlinburg firestorm showed what a mountain wave downslope wind can do to a drought.

The northeast corner is the highest, coolest and most sheltered part of Tennessee — the Blue Ridge blocks so much of the Gulf's moisture that the valley floor is among the driest ground in the eastern states, while the peaks above it are among the wettest. When the flow turns northwest behind a front, the mountains squeeze out upslope snow the rest of the state never sees; when a tropical system stalls on them, as Helene did in 2024, the Nolichucky takes the whole county with it.