When I was hiking the PCT (Pacific Crest Trail) and stopping at Mojave for a resupply, an old man told me, “When the skies get dark, climb high”. It was a warning about flash floods in the desert.
Later I heard about a thru-hiker that camped in a dry river bed that year. He said that there were campfire rings in it and it looked well used for camping. That night he was woke up by a strong pressure pushing on him. He fought his way out of his sleeping bag and tarp to swim out of the way of the water. He said that if he had been in a tent he didn’t think he could have gotten out. He lost everything. And hiked into town with nothing but a t-shirt on. He also said that it wasn’t even raining where he was; the water must of come from rain up in the hills.