Year around I wear a yellow and black Cortech GX-Air. It is hot when you are sitting still but since it is mesh, it has a nice air flow even on 100 degree days. It is not as hot as the sun on my bare skin. I selected the yellow for visibility and might might a gray one next time. I have gray over pants and they are cooler than dark jeans.
In the winter, I use the zip in liner which itself has a zip in water proof liner. It's good down into the 40's with a warm shirt.
