The driver side footwell of my '19 Fit has ~1/2 of water after a hard rain...Only the second time this has happened...I do not see anywhere where it might be leaking...Water is only on the floor. Everything on all sides seems to be dry...I had not driven the car for a few days...I've snooped around some and see no indications of leaking anywhere...Any ideas out there?...Thanks...

 

You can get water intrusion through the door itself. There is a plastic seal behind the door card (the part you see inside the car). If that seal is breached or broken water that runs down the window and inside the door can enter the car, especially during a hard rain.

 

...Thanks Drew...I will investigate...

 

Two other quick thoughts (that I didn't think before):
1) Take a look at the window sweeps on your door. They can degrade over time (or fail/break away completely), allowing more water to run down the windows and into the door.
2) Make sure the drains at the bottom of your door aren't blocked. I suspect you would notice if they were, because a door with water inside would be heavier than normal, but if the door isn't draining from the bottom it will eventually start draining behind the door card and into your car.

 

...After further review & agonizing inspections (it's been 95'F), I've narrowed the leak to the left corner of the floorboards (where the firewall & kickboard meet)...I can see the water running down that corner but have not the pinpointed the exact breach...The reason I never saw or felt wetness on the sides of the footwell is because it was travelling down the corner behind the left foot rest...Inspections will continue...

 

...So...I've had enough of this bullshlt...I have determined, (pretty much), that water is not leaking on any electrical...The water is running down the corner behind the left foot pad which has a thick styrafoam backing...I carved out a viaduct on the back of the styrafoam & drilled 3 1/4" holes in the bottom corner floorboard...Guess we'll see what happens...Oh...By the way...I tested again this morning...Dumped ~5gals of water on the left side windshield...You know...That sob didn't leak a drop...Hence my radical modification...

 

here is most likely your answer for anyone who may search this later. my 2016 fit has has this happen more than once and on either side. If you pull the bottom of the plastic fender liner and look underneath you will see a place when water comes forward and out normally. theses get clogged up with mud and the inside area overflows with water with heavy rains. I just basically took out the retainers on the bottom half of the inner fender and took a hose and put high pressure top the area backflushing it until it looked clear. I have done this three times in 5 years.

 

...Something else to investigate...When it cools down some...Thanks...

 

I have had this exact same issue. Everyone says its the drain holes but it is much more than that. I pulled out the plastic parts under my steering wheel and discovered the water is coming coming from somewhere and dipping below my cupholder on the left side.Then it makes its way all the way down to my floor. If you find a solution , please post it.

I may have to go to a Honda dealership.