Great Lakes Marine Forecast Zones

How Great Lakes marine zones are organized

The National Weather Service divides each Great Lake into named coastal forecast zones — typically a 20–60 mile run of nearshore water between two harbor anchors (e.g., St Joseph to South Haven, Marquette to Munising). Each zone has its own UGC code (LMZ for Lake Michigan, LSZ for Lake Superior, LHZ for Lake Huron, LEZ for Lake Erie) and is the smallest unit at which NWS issues Small Craft Advisories, Gale Warnings, Storm Warnings, Hurricane Force Wind Warnings, Special Marine Warnings, and Beach Hazards Statements.

Forecasts and warnings are issued by the regional NWS office responsible for that stretch of shoreline — NWS Grand Rapids (GRR) covers Lake Michigan from St. Joseph north through Holland, NWS Marquette (MQT) covers most of Lake Superior's south shore including Pictured Rocks and Whitefish Point, and NWS Detroit/Pontiac (DTX) covers Lake Huron and Lake Erie. The page for each zone shows currently-active advisories pulled live from the NWS public API, the zone's geographic context, the cities and ports along that shoreline, and which Michigan counties border it.

These zones matter for recreational sailors and powerboaters launching from Michigan harbors, for commercial freight crews routing through the Great Lakes shipping lanes, for harbormasters and marina operators deciding when to limit small-craft access, and for any resident of the lakeshore counties — Berrien, Van Buren, Allegan, Ottawa, Marquette, Alger, Luce, Chippewa, and others — whose summer recreation, fishing economy, or property is exposed to lake-driven weather. When an advisory is active for your zone, the live page surfaces the full NWS bulletin alongside the issuing office's marine forecast portal.