I finally got to experience a full day's riding in 90+ weather this past Saturday sporting my Sahara jersey and pants and those things definitely make a difference. When I was done for the day, my legs weren't soaking wet like they were in my normal pants.
The jersey held up nicely, although I did notice a mild sunburn on my back the next day. Nothing serious though. I'm fair-skinned and it was gone the next day, not even any soreness.
I packed a towel in the ice chest and that thing was amazing. I just threw a few ice cubes in it, rolled it up, and put it around my neck between rides. I can honestly say that sitting in a chair in full gear (minus helmet, gloves) was completely comfortable, even when it was over 90 degrees.