The Arizona sun is no more UV intense than the Colorado sun in summer, and a good, high SPF sunscreen is all that is really necessary. I use 30 or 45 SPF, and with them I have trouble getting any sort of a tan at all, much less a sunburn. I couldn't stand to play in midsummer if I couldn't wear shorts and a polo.
The Denver area tops out at over 100 degrees too in the summer, and that added to a 5000+ foot elevation makes for a very intense sun.
