On Lake Winni the Spring is usually the best for Ice Boating. I have Ice Boated on Winni
after April first. The bob houses were gone leaving large open holes that had to be avoided.
The snow ice starts to settle every day in the sun and freezes at night. The next day the frozen snow ice will support the runners until....such time as the snow ice turns to snow again. The transition is almost instantanious..back to snow...a
Phase Shift.
If you were not prepared you will NOT Sail. You will be relegated to walking...towing the boat behind you...maybe miles. Most of us would carry an Extra set of special runners designed to slide over/through transitional snow ice.
Sometimes..areas of the lake would Ice Out all together and refreeze over a day or two... yielding NEW Black Ice. I have 35mm photo slides of 15 or so ice boats on the east side of Rattlesnake on 4 inches of new black ice. Those were the days.

NB
EDIT: I really need to convert all my 35 mm Ice Boating slides (1970s) to digital format on CDs so I can post them. I have tried photographing them off a projection screen with a digital camera. It does work, but not with the best quality.