floor wet behind passenger seat on 2005 Volvo S40

Just discovered behind the passenger seat floor is sopping wet. Took the floor mat out and trying to air dry the area - I have no idea what has caused this - we have had a huge amount of rain lately and the car is parked in driveway (no garage). Any help would be appreciated.

Asked by for the 2005 Volvo S40
Volvo has a service bulletin regarding this issue, there is a "water intrusion behind the windshield" That's the exact phrase they used. Bring it to a Volvo specialize shop to have it repaired, this is an involved process.

Tell them this service bulletin number: RTJ14545-2008-10-07
1 more answer , 1 more comment
I had the same thing.
It was the sunroof drain there are two - one in each front corner of the sunroof.
You can see them if you put the sunroof back.
They are a hassle to get to and I couldn't get any wire or anything down them to clear them.

What worked was putting a drinking straw in the hole and blasting high pressure air (from petrol station forecourt) down them.
I've had the same problem. Performed the same forced air thru straw. Air came out just below windshield same side.
The other online discussions indicated a connection between drain tube at right side in post bottom of windshield. It is raining today so I should see if the forced air was sufficient to correct or will I have to take interior post trim off to verify connection at end of tube from sun roof.