For warm weather trail running - and other assorted aerobic pursuits - the attributes you need in your clothing are low weight, breathability, the ability to shift moisture, sun protection and seams which don't chafe. Durability doesn't hurt either!
Challenge accepted: presenting the Ar'teryx Accelero Comp T-Shirt, weighing in at just 132g.
Mesh over the shoulders and back enhances airflow. A durable, smooth knit front panel (with a UPF of 50+) and carefully positioned flatlock seams fight chafing. A wicking finish promotes rapid evaporation of moisture. There's even a natural stretch in the knit of the fabric for enhanced freedom of movement, and an antimicrobial odour control treatment.
So that's the ticklist done and then some!