Can only speak for me here in Arizona...my "lightweights" are my SportKilts, but they're tartan. For yardwork I'd go with Utilikilt Originals. AmeriKilts are also good light weight kilts for summer.

For fancy stuff my 11 ounce lightweight tank from Kathy's Kilts is still cool in the summer.

Heck, even my leather kilts are cool in the summer. While they hold heat in the winter they seem to circulate it in the summer. Go figure.

Ron