Springtime in Michigan? It seems to go from Winter right into Summer. March is COLD. April, some nice days, but more likely it's freezing at night and snow storms are not uncommon. May starts to warm up, but still some frigid nights. That, plus the kids are still in school, so there are no crowds. After school is done, all bets are off!
In Michigan, Memorial Day is the unofficial beginning of Summer, even though there is a chance there may be one or two frosty mornings in the first couple weeks of June in the northern parts of the Lower Peninsula. Heading into the Upper Peninsula, the later the better. Frost is not uncommon in June, then the flies come out. Late August through September is absolutely stunning in the UP.
All that said, if you have a furnace and your trailer is kept reasonably warm. you shouldn't have any problems in late spring. By the way, Michiganders like to go to Atlanta and beyond in the Spring for good reason!!!
Some dates are here:
https://www.victoryseeds.com/frost/mi.html