I think our conditions are similar to some extent, daytime temps here are above 95 degrees, however while moving at highway speeds I don't seem to have a problem, however once you get into stop/go traffic my gauge reading escalates rapidly to well over 220 degrees, and sometimes a bit higher. The oil gauge also shows very low pressure when operating at the high coolant temps.
I've not had the coolant loss issues you've experienced yet, however I did have to add about a third of a gallon to bring the sight-gauge on the coolant tank up to the full mark.
I hope this is not signs of things to come, here in the valley we have not yet seen our normal summer temps of 105 degrees plus.
Anyone else seeing fluctuations like ours, or is this a California thing?