Not original commenter, but, I was able to look at the Apple Weather forecast right before I napped at 2pm Friday. The forecast then pretty much said showers for a few hours that day, but definitely was nowhere close to the amount of rain that actually fell. The weather there can be unpredictable.
I took a photo of the forecast on Thu to show campmates, this is what it looked like then: https://sincere-zenith-02b.notion.site/Forecast-Photo-88c591169ea74fd7961136a7f4409a63. Friday was the day with the heaviest rain.
A crew of people is there for a whole month before the event starts, and it pretty much always rains at least once that month, and we read about them having to stop work, shelter, and avoid medical emergencies. This year, Tropical Storm Hilary passed through a week before the event start, and the community as a whole was keeping a keen eye on it.
You may have seen the word 'playa' in reference to the event grounds. In the general English context, 'playa' means 'dry lake'. The entire event is literally held in a dry lake. If you want many square miles of ground that can sometimes be asphalt-like, you go to a dry lake. And for the land speed records, it also happens to be super flat. It's the accumulated standing water that does that.
It’s widely known to most attendees how impassable Black Rock Desert is when it rains. My camp and all the camps around us had food and water for at least a few extra days, and we had more than adequate morale the entire weekend. This year, I personally brought at least 2 weeks worth of kilocalories, and packed 3 raincoats. I handed out 2 of the raincoats to campmates pronto.
If you look at the back of the event's paper ticket, and then the official survival guide, for this year, and years prior, they mention rainstorms, and what to do in such a scenario.
Wait til you see Republicans take credit for the promotions.