Dammit, this exact thing happened to me today, but with a different question. My family and I were driving from Palm Springs back to Los Angeles through the San Gorgonio Pass, one of the windiest places in the country. My daughter asked “What makes wind?” and I told her that since hot air rises, this creates a vacuum for cold air to rush into. Since the air in the desert is consistently hotter than that near the ocean, there is a near-constant wind rushing through the pass to get from the ocean to the desert.

She paused for about five seconds and then asked “So why does hot air rise?”