Water leaks from nowhere after the rain inside my Pontiac Grand Prix '98 SE

Water can travel down gullies and channels. Water the windshield area.

You may want to remove all the trim at the cowl area while you try what Paul said. GW

maybe sit in the car when it rains, lol....maybe you have a crack in your windshield or it is not sealed properly around the sides.

had same problem with my 97 grand am. when they were built , the firewall didnt meet proberly with the indide of car. they tried to use sealant to fix problem , some worked some didnt, not enough for a recall though, i had water comning in from nowhere, could not figure out either, pull downthe rug around firewall get a buddy wtih flashlight from under hood and use a good sealant from auto store, use black so the light wont shine thru

have u had the AC drain hose checked?

If you have a sunroof on your car you may want to make sure the drain channel and its drain lines are clear. Sunroof drains are suseptable to clogging from foreign objects/debris.

Sounds like a blown out heater core.

I recently had less water than you stated, but also in the same region couldn't find where it was coming from. (my car pontiac grand am)

I had hole in my firewall a little larger than a size of an egg I could see it by looking in the hood...

I recently had less water than you stated, but also in the same region couldn't find where it was coming from. (my car pontiac grand am)

I had hole in my firewall a little larger than a size of an egg I could see it by looking in the hood...