While there’s a chance to hear them anytime of the year here, the “best window” to pin down their territory wraps up about now.
“In Minnesota, calling occurs in all months of the year, but most frequent in Feb and early Mar, prior to egg-laying (Dunstan and Sample 1972). Another peak in late summer and fall possibly corresponds to dispersal of young.” – Birds of North America
This is the other common owl species I’ve only seen in my atlas block (never heard), so I hope to get lucky and spot another one.