I don't think that you are crazy at all to visit the Grand Canyon in August. Sure, there will be crowds. But that is because this is one of the most wonderous sites on the planet! If you have never been, you surely should make the effort if you are going to be so close.

With regard to weather, you will be at 7000 feet of elevation on the South Rim. Even in summer it is not too hot, maybe highs in the 80s. In fact, evenings can be pleasantly cool in the 50s. People who hike or ride burros down into the canyon experience the blast furnace hundred degree temperatures.

The air quality can be so-so, but not because of LA smog. There is a coal-fired power plant not far from the Grand Canyon. It produces the haze that can result on some days in not being able to see across the canyon.

Absolutely the two best times of day to visit are sunrise and sunset. The colors in the sandstone are vivid, the shadows create amazing vistas, the temperature is comfortable and the tour buses have either not yet arrived or have left. I recommend that you plan your visit to experience one or the other.

Mark in Los Angeles