Eric,
Yeah, us being from Southern California, we don't turn on our A/C until it hits at least +85 degrees F. OTOH, we are wimps when it comes to *winter* if you can call it that. We have restaurants that have outdoor heating if the temperature drops down to a *chilly* +65 degrees F. Most folks in the Upper Midwest would likely call it a nice summer evening and put on shorts and a t-shirt with flip-flops.
If touring in middle-of-nowhere I highly recommend lighweight Merino wool. Being of the lightweight variety it isn't too hot to wear and it dries out quickly if left in the sun (after washing). It is anti-microbial and it doesn't smell as Joe M. points out. Wool top + wool boxers at least for me was a great combo. One could go for multiple days without having to bathe (had to purify water for drinking and cooking only). This was a great combo for the Great Divide where services were relatively far apart. Smartwool was where we bought most of the our clothes from.....
Be advised that many call their garments *wool* when in fact they are wool-blends. To get the less-stinky garment, it is important to get a mostly if not 100% wool garment.
Jeff
Claremont, CA