Well the best hours for uvb are between 10 and 2. It diminishes as the day goes on especially toward the evening. How are you keeping your chameleon outside all day? I live in south florida and I know my temps are not that different from yours. I think it is way too hot to leave out all day. Do you have an automatic mister to cool your chameleon off? How old is your chameleon? I periodically bring mine inside ac to cool off. It is just too darn hot out. There is no place to cool off down here even in the shade. I would be very careful and monitor your chameleon closely. As far as the UVB, is it filtered through the Lanai and then filtered again through your cage?