Water level
870.98ft NGVD29
-0.10 ft in 7 daysOct 11Oct 18Oct 25
Sep 25Oct 10Oct 25
Reading from Oct 26, 2026.
Grand Lake St Marys was at 870.98 ft on October 26, falling 0.10 ft over the past week.
Right now on Grand Lake St Marys
loading
Best window
0pm to 0pm
score
Wind
00kt
Gusts 00
Direction
NE
Blowing from
Air temp
00°F
High
Rain
Dry%
next 6 hours
Water level
870.98ft
Down 0.10 ft this week
Sailing
CheckingReading the forecast
Kayak and SUP
CheckingReading the forecast
Power boating
CheckingReading the forecast
Fishing
CheckingReading the forecast
Hour by hour
Next 24 hours
Wind and gusts0 to 30+ ktScoreGood, caution, stay ashoreNightBest windowArrows point where the wind blows to.
Outlook. Monday: WSW wind 0 to 3 kt, gusts to 6 kt, high near 72°F. Tuesday: ESE wind 2 to 5 kt, gusts to 9 kt, high near 71°F.
7-day wind forecastLive radar
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LightHeavy
Last hour of NOAA MRMS radar, 1 km resolution. Map data © OpenStreetMap contributors, OpenMapTiles, OpenFreeMap.
Lake facts
- Type
- Reservoir
- State
- Ohio
- Surface area
- 12,846 acres
- USGS gauge
- 403204084342601, Grand Lake St Marys near Celina OH
- Coordinates
- 40.5300° N, 84.4900° W
Background reading: Grand Lake St Marys on Wikipedia
About Grand Lake St Marys
Grand Lake St Marys covers about 12,846 acres in Ohio and is classed as a reservoir.
We read the level from USGS gauge 403204084342601, listed as Grand Lake St Marys near Celina OH. Wind and weather come from the National Weather Service grid cell over the lake, so the numbers describe open water rather than the nearest airport.
On a lake this size the wind has miles of open water to work with, so a 15 kt breeze can stack up a steep chop in the main basin while sheltered coves stay flat. Reservoir levels move with releases and inflow, so ramps and beaches can change week to week. The water level page tracks that day by day.
The go or no-go calls above are a starting point, not a guarantee. Read how we score conditions, and always check local rules and posted warnings before you launch.
Grand Lake St Marys questions
Is it windy on Grand Lake St Marys today?
The National Weather Service forecast for the lake from October 26: Monday: WSW wind 0 to 3 kt, gusts to 6 kt, high near 72°F. The panel at the top of this page refreshes the current wind, gusts and direction when you open it and turns them into a call for sailing, paddling, power boating and fishing.
What is the water level at Grand Lake St Marys right now?
Grand Lake St Marys was at 870.98 ft on October 26, falling 0.10 ft over the past week.
How big is Grand Lake St Marys?
Grand Lake St Marys covers about 12,846 acres (20 square miles) of surface water.
Nearby lakes
If Grand Lake St Marys is blown out, these are the closest alternatives. Tap through for their conditions.