We are having issues with flies swarming on the sides of our home and lawn.Any suggestions on how fix this?

There is no garbage or compost stored anywhere near by, but we are still having a problem with flies swarming all over our home and lawn. Does anyone know why and also how to help in the removal of these pests. We live in Central NY state and have just started having warmer days. They seldom come into the house but it still makes enjoying the outdoors next to impossible at the moment.