Just had a lot of rain. Water was leaking into

sometimes even when seals look ok,they are not.

several qs. What year make and model is the car? Is car level when water fills floor? Does it always happen every time it rains fairly heavily? Is the trunk always dry? Talk to other owners for their experience.

A water leak under the dash could be the heater leaking near the glove box, or a windshield leak, or sometimes the drain tube for that area has gotten plugged up and needs to be cleared out. Most times a little blast of air pressure will do it.
Hope this helps.

Leaking trunk seal or rear window sealer also check the tail lights are mounted properly and that the trunk is closed all the way

does this happen only after it rains?
check under the wheel well or near by for rust the other place maybe around the rear window seals leaking in under them.

Answer is no. The weather stripes around your door or your rear wind shield are leaking. also if your trunk channels are full of leaves and trash will cause improper drainege. Put someone inside after cleaning and checking the above. Have someone runa light sprinkle on the rear of the car. using a flash light try to find your leak. Or another process is to use a stick of insence or one of those fire cracker sticks start the car select manule mode without recirc. on ventalation system. turn blower to high, and close all windows and doors . Pass smoke near all seems and seals. you will find your leak when the smoke gets blown away from the seem.

water leak at the roof ditch moulding, the rear window seal, or the moon roof drains being plugged.

Does it do it without moving the car? Could be water splash in the wheel well through a sealer skip in a seam.

Facing up hill or down hill or both?

Lift up seat cushion and lift carpet and follow water stain path to source.

See if you have a WATER DOCTOR franchise near you. They keep a record of common sources of leaks for their repair techs.

I think I'd take a minute and stop at an autoglass place & get their opinion on it. Sounds to me like a bad seal at base of rear window. Keeping in mind, you don't have to agree to an expensive fix, if it doesn't sound right.

i had the same probmlem its coming from one of 3 lights is the center quick fix was to use clear silicon from wal mart .. also it can leak from the moulding near the corners of the windsheald but rare...

The most common source of this kind of leak is the windshield, have a glass shop check the sealing around the glass