When we get "cloud cover" it is absolute. To the point of disrupting "SKY" Mexican TV satellite coverage for the kids. Don't know about anyone else but the neighbor's panel will go from around 7 amps to 9 amps when cloud edging then drop to .7 amps charge rate when the cumulus blocks the sun then fills the sky - a 90% reduction.
The only way I've found to get 100% guaranteed service, is to ring down for room service. "Camping" implies a certain amount of risk, uncertainty, and discomfort. Horse packing was involving to the extreme as far as planning was concerned. I had a friend who poo-pooed my advice and pointed his tent opening to the southwest and did not bother to zip it closed - it took an hour to trudge back to camp through a heavy September snow squall. His tent was filled with wet snow. Much of his anger was embarrassment I would believe.
Plan for the worst and enjoy the best....