have settled on the rapha merino wool base layers for the last decade +. have worn them to a low of 33 degrees and a high of 107 degrees.
both the short sleeve and long sleeve ones have lasted for the better part of two years when using 2x a week (gentle machine or hand wash-no dryer!!).
these days, i buy two at a time every other year to defray the wear and tear on any one particular garment.

ride mostly in southern california...beaches, foothills, deserts, mountains. obviously not the most humid area but the short sleeve ones work well
even in the triple digit heat range. yes, you're a little hotter but if you've got access to water besides what you're carrying on the bike, soaking it and then
putting it back on feels great. occasionally got a few sunburns through lightweight jerseys in the days before always wearing a base layer. haven't had a
sunburn through a lightweight/hot weather jersey since.