I wear a tourmaster flex jacket. It has a liner for warmth, and a removeable outershell that leaves it a mesh jacket. I usually wear a wool or fleece sweater for the warm layer instead of the liner. Then I can use the the sweater off bike as well.
Wore the mesh this weekend in 90 degree weather. It was warm, but not bad except at stops. I was on the back of my husband's bike that day. He kept having me dump water down his back...auto cooling system
kari