Spring maintenance
Check the roof and flashing for winter wear, clear gutters and downspout extensions, regrade soil that has settled against the foundation, test the sump pump before the wet season, and have the AC serviced before the first hot stretch.
Summer maintenance
Watch for basement humidity and condensation, run a dehumidifier where needed, inspect deck framing and ledger connections, and check exterior caulk and paint that Minnesota's freeze-thaw cycles open up.
Fall maintenance
Have the furnace and heat exchanger inspected before heating season, clean gutters again after leaf-fall, disconnect and drain exterior hose bibs, seal air leaks in the attic, and confirm attic insulation depth and ventilation before the snow load arrives.
Winter maintenance
Watch the eaves for ice dams and icicles that signal attic heat loss, keep the attic cold and well-ventilated, monitor for condensation on windows, and keep snow cleared away from foundation walls and basement window wells.