Just experienced this myself. It was condensation occurring at the same time as the rain but usually when it was a heavy down pour. We were camping on the east coast and the condensation came from the fog that rolled in on some days, or moisture from my CPAP machine Humidifier. Overnight temps often dropped to 11 to 13 C. I've also been in a couple of down pours since and not had any issues.
Wayne, Kim, Mallory & Abby the Dog
2013 - Jayco Jayfeather - X20E
2012 - Toyota Tacoma DBLCB Sr5 with towing package
Equalizer 10k WD, Prodigy P3 Controller, TST TPMS
2012 - Jayco Sport 10 Popup - Traded