Some winters, a winding line of old Christmas trees appears across the frozen Straits between St. Ignace and Mackinac Island. Watch the weather and the ice that make this remarkable island tradition possible.
Keyless CARTO map + NOAA analyzed ice layer
The Straits have moving currents, cracks, pressure ridges, wind-driven ice movement and shipping activity. Christmas-tree markers are not safety certification. The map deliberately shows no crossing line, and a Coast Guard restriction on vessel traffic does not authorize travel on ice. Mackinac Island Tourism discourages ice-bridge snowmobiling.
Cold weather may encourage ice growth. Wind, currents and moving water can change the result.
Awaiting NWS hourly forecast.
Select a day to compare freezing and thawing hours, not to estimate a safe crossing date.
Blue bars represent forecast hours at or below 32°F; tan bars represent hours above. This is air temperature at a nearby mainland forecast grid, not an ice measurement. Wind values are forecast maxima, not observed gusts or a mechanical ice-strength model.
A cold afternoon is a moment; several days of subfreezing weather are a process. Follow the consecutive freezing hours, then look for warm spells that interrupt them. Even prolonged cold cannot certify strong ice across a channel.
Currents, changing wind and boat traffic can open leads, move whole sheets of ice and make nearby places look completely different. That's why a smooth-looking chart cannot answer whether a snowmobile can travel.
NOAA charts estimate how much of the water surface is ice-covered. They do not sample every crack, pressure ridge or hidden current. Treat changing map colors as an ecological and seasonal signal, not a route recommendation.
Visitors know Mackinac Island for its summer bicycles and horse-drawn carriages. Winter belongs to a smaller, year-round community. When the waters between the island and St. Ignace freeze, island residents have traditionally marked a snowmobile ice connection with discarded Christmas trees.
The trees are striking—a small winter forest standing where ferries travel in summer. But they are not an official highway. This tradition appears only in favorable winters, and even then the ice can change suddenly.
Mackinac State Historic Parks notes that nineteenth-century winter ice supported fishing with nets and poles; the Christmas-tree line is a much newer expression of life on the same unpredictable water. Read the Parks' historical account ↗
Try watching this forecast each week. Is the air holding below freezing? Does wind strengthen? Does the NOAA chart finally show ice across more of the Straits? The story is in the changes, not one green checkmark.
These are verified historical events, not current bridge conditions.
The Coast Guard's Northern Great Lakes Captain of the Port closed the waters separating St. Ignace and Mackinac Island to vessel traffic to facilitate ice growth.
Coast Guard notice ↗The Coast Guard reopened the waterway. A shipping restriction is an administrative navigation decision, never an authorization to cross ice.
Coast Guard announcement ↗Coast Guard Cutter Mobile Bay was scheduled to begin breaking ice between St. Ignace and the island, a reminder of how rapidly conditions can change.
Coast Guard announcement ↗Observed ice and forecast weather are different products, intentionally kept separate. Refreshes request current data; when a feed fails or is stale, the page shows unknown rather than guessing.
NOAA analysis is region-scale and may be absent outside winter. This tool does not measure ice thickness, predict tree placement, verify whether an informal route exists, or provide instructions for crossing. Explore Michigan's wider ice report →