My water heater propane side will fail to light at times during thunderstorms and heavy rain. It did it again last night when weather moved through. I just reset the switch and all is well now. I have found through the years that when this starts to happen I go out to the heater and blow off the gas orifice, venturi tube, and burner tube with compressed air as well as the spark electrode. This eliminates the problem for a few weeks/months and then I have to do it again. No big deal and easy fix.
2006 GMC 2500HD CCSB 4x4 Duramax/Allison, Titan 52 gallon fuel tank, Prodigy Controller, B&W Companion Hitch
2010 Jayco Designer 35RLTS, Cummins/Onan RV QG 5500 EVAP, Progressive Industries EMS-PT50C, TST Systems 507 TPMS, RV Flex Armor Roof