Grand Lake St. Marys Radar & Lake Map

Grand Lake St. Marys is located in Ohio at coordinates 40.5300° N, 84.4900° W. These coordinates represent the hydrographic center point verified against the USGS Geographic Names Information System (GNIS) and National Hydrography Dataset (NHD).

Our real-time lightning radar monitors electromagnetic atmospheric discharges within a 30-mile radius of Grand Lake St. Marys. Concentric safety rings indicate proximity: 5 miles (critical danger zone), 10 miles (15-minute arrival warning), 20 miles (basin caution), and 30 miles (perimeter monitoring). It tracks storm bearing, flash density, and evaluates the marine 30-30 safety rule.

The live radar overlay displays a real-time 6-frame precipitation loop powered by RainViewer and NOAA NEXRAD Doppler radar composites. It updates every 10 minutes to show incoming storms, rain, snow, and thunderstorm cells directly above Grand Lake St. Marys. You can pause, play, or scrub the timeline using the controls in the top-right corner of the map.

Grand Lake St. Marys features multiple shoreline access points. Launch sites typically provide concrete ramps, docks, and parking, though seasonal water levels and park permits may affect launch availability.

Grand Lake St. Marys has 4 mapped hydrological sensor stations. For continuous 30-day water level history, full-pool comparisons, and water temperature trends, check our dedicated water telemetry page.

Our Weather & Forecast page delivers 24-hour hour-by-hour wind timelines, peak gust forecasts, watercraft safety thresholds, and 7-day marine outlooks sourced directly from the National Weather Service.