The rain began in eastern Texas and eastern Oklahoma on Sunday, and it's not stopping any time soon.
Some spots in and around Houston have already seen more than 10 inches of rain.
The rain doesn't appear to be slowing down, either.
A front is stalling over the southern Plains, and now that area is bracing for days of heavy rain and thunder.
The heaviest rain will fall along the Gulf Coast of Texas, but significant rain will spread out as far as central Texas up to the eastern half of Oklahoma and into Arkansas and Louisiana.
Rainfall totals like these don't happen often. Some places in Texas, Oklahoma, Arkansas and Louisiana could get two or three months worth of rain in a matter of two or three days.
The National Weather Service has already issued flood watches and warnings from southern Texas up to southeast Oklahoma and southwest Arkansas.
And with the current forecast, it won't be until Thursday or Friday until the rain finally moves on.