I've been to LAS where it's 110 degrees and the plane is an icicle. The secret is keeping the hose off the ramp. Most other airplanes are higher up and thus the hose touches less of the ramp. Whereas on 737 it's so low the whole hose bakes and lukewarm air comes out.

Dimming the screens has been unwritten sop for years and automatic for 99.9% of the guys I've flown with...just a lot of new guys on the plane in recent years that don't know better.