I too wear baselayers all year here in Ohio, riding or not. My two favorites for summer are Defeet Un-D-Shurts and Under Armor Heatgear compression tops. I have all three styles of the Defeet, sleeveless, short sleeve and long sleeve. The UA Heatgear is long sleeve. I've been wanting to get the sleeveless version, but keep "forgetting". These work in the summer because as I sweat the fabric gets wet and the airflow of the ride creates a evaporative cooling. Air blowing through wet fabric against the skin = a nice chill. Even hot air. Take this morning for example, some low 70's degrees and humid, sunny, light wind. A Defeet sleeveless shirt under my tight fitting Sportful jersey and bibs. In the sun I'm hot and lightly sweaty. I descend into some heavily shaded ares near creeks where it's notably cooler, and the chilling effect is pronounced. I zip up my jersey all the way to stay warm. If you're not accustomed to wearing a baselayer shirt, especially a long sleeve one in hot and humid conditions, you will feel like you're almost overheating at first, until you start sweating and the fabric starts getting damp. Then you reach a perfect point of comfort. Also, if you stop for a minute while riding in the heat and if there's little wind, you'll also be quite hot until you start moving again. I've never felt even the long sleeves were too much while riding. Again, wet fabric with wind blowing over it = evaporative cooling effect. Long sleeves also keep the sun off your arms and they don't heat up like they do with short sleeves. When done with the ride your arms feel "normal" temperature. In all of this I'm referring to form fitting clothing, "second skin" like.

Duly noted, I'm a summer heat lover, I love summer, I love summer, repeat infinitum. I can even be sitting out in 90 degrees and humid and love it. Spray myself with a hose, of even warm water, add some good wind, and to me it's comfortably cooling. Needless to say, in the cooler season, controlling the wind flow from passing over sweat is a must for me, and there's a fine line between between "too much" airflow and "not enough".