You did in fact get lucky with the weather. Snow is not unheard of in the late spring. I can remember getting snow while camping on the first day of summer a few years back. It all melted off, but it was cold and snowy on that trip.
When I lived in SoCal (near sea level), I used to wake up early (3am), drive north to Mammoth, and on the same day ski from the top at 11,053 feet above sea level without ill effect. Those were good, wild days. Admittedly, the Summer days when I drove to the same area and hiked into the backcountry (sometimes to greater heights) with a heavy pack were a little more taxing, but never debilitating. I feel fortunate not to suffer altitude sickness.
