I know what you mean. I too have had hundreds of troops out on parade grounds all day. Not a single fall out or issue. The troops are told to pre-hydrate and we kept an eye on them. Water was available throughout. Sitting in a shaded arena and listening to a devout Marxist would give me nausea and vomiting, but it wouldn't be due to heat.
If anything, passing out would be a blessing under those circumstances. I know that after the first hour, I'd have locked my knees and started counting backwards from 100,
Before you can do things for people, you must be the kind of man who can get things done. But to get things done, you must love the doing, not the people!