For starters, an open-weave knit makes an excellent swim cover-up, and a lightweight cardigan can help you combat overactive office AC. To expand your outfit options, we’ve shortlisted the best summer sweaters that will aid in the upcoming transition to fall. The Cotton PulloverCool summer mornings and nights are what cotton sweaters were made for. The Nautical Stripe SweaterNautical striped sweaters are a summer classic. The Featherweight CardiganUnseasonably cold summer days call for an ultra-lightweight, breathable cardigan.