Hurricanes are huge, spinning storms that form over oceans. They move across the water and usually weaken once they reach land. But Harvey acted strangely. It got caught between other weather systems. That caused it to sit in the same spot, dropping more rain in a few days than the area typically receives in an entire year. That allowed Harvey to do a lot of damage.
As the rain began to pummel southeastern Texas, floodwaters quickly rose. Rivers, reservoirs, and bayous—channels that crisscross Houston to remove excess water—quickly overflowed their banks. Roadways and neighborhoods soon became swamped by several feet of water, stranding people inside cars, homes, and businesses.