If the situation permits a laid-back outfit, wear a black open cardigan with black chinos. Play up the dressiness of your ensemble a bit by rounding off with black leather desert boots.
Black Open Cardigan with Black Chinos Warm Weather Outfits
For something more on the cool and casual side, wear this combination of a black open cardigan and black chinos. Grey canvas low top sneakers are a good pick to finish your look.