Yeah, for the most part I think mesh only makes sense from around 80-95, and then only for short sprints at 95. In some places, like the middle of NC, that means mesh works for a substantial part of the year. In other places mesh might be a waste. If your mesh jacket has chest pockets (like most of olympias do), try filling them with ice at stops - works much like soaking your shirt. I have an evap-o-dana, it seemed generally helpful at 95, or 95 on blacktop (so probably 100 or more), but I think it would really shine in higher temps, as any time I hit a pocket of cooler air the evapodana felt like it was blocking it.