Wind/fan noise from the back when road is wet?

A few days ago I heard a noise coming from the back of the car that sounds very similar to the wind noise when a window is open. But all windows were closed and I confirmed it wasn't the radio. I opened and closed all windows the noise was still there. It was not there when the car was not moving. The noise also sounded like air going through a vent. I checked the high battery temperature with ScanGauge. It was only 19C (66F) and I have never heard the battery fan coming on even during the hot summer. I checked all glass and none was broken or cracked.

Now the noise is gone. The only difference I could think of is that when I heard the noise it was raining and the road was wet. Could it be the wet road noise? Anyone has similar experience? Thanks!