Was the door sil removed the last time it rained hard ..??
(I don't reckon your A/C was running while you were at work ..... so, how could that be it ...
)
Are you sure your drivers side window was all the way up ... ??
I'd suggest you put a hose to the car and see if you can find out where the water is coming in.
I hope you get it figured out.
humfrz