Due to multiple factors, expect to potentially pay more when booking in March. For low rates, June can be a great choice for travel to Appleton. Flights to Appleton from Sioux Falls in June are about $299 on average during June, but can be found for as low as $143.
Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Sioux Falls to Appleton as you normally would.