Depending on your location, varmints might also be an issue! 
I'm now in Phoenix and I put my veileds outside for as long as possible in the cooler times of the year.
My last veileds were doing exceptionally well during the spring and early summer. I would *not* recommend putting them outside during mid summer. You might be able to do it for a couple of hours in the late evening, but please be very careful. 100+ weather will kill your chameleon in less than an hour. Sadly, I know this first hand.
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Victor Gomez
gomezvi@yahoo.com