I'll draw on my experience living near one of the places in North America with the widest summer to winter temperature range ... Winnipeg.
We sweat in summer and in winter, and cotton collects and retains sweat.
In winter, that's not great. I've worn cotton as a baselayer for both cycling and cross-country skiing, and it gets soaked and really uncomfortable.
But after years of experience, I have nailed down a winter cycling combo I like.
However, in summer, it can be just what we want. In fact, I (and people I've ridden long distances with), would even run our light, white cotton T-shirts under taps when we found them to make them wet if our own sweat wasn't doing it.