Yes, but not all types of turtlenecks can be worn in summer for obvious reasons. And there are some that are more than just okayish to wear in summer because obviously not all turtlenecks are created equal!  The ones called mock necks are often made up of lightweight cotton or even flannel; they are great to rock in summer. They can be worn instead of a tee and they look great with chinos and jeans. Then there are other types of turtlenecks that are in fact summer staples. Like the short sleeve turtleneck, or a turtleneck tank top.