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Official National Weather Service (NWS) point forecast and real-time wind conditions for Grand Lake St. Marys (Ohio). 24-hour hour-by-hour wind timelines, peak gusts, watercraft recreation safety thresholds, and 7-day marine outlook.
Today: High 76°F · Low 59°F
Peak gusts: 15 mph · Lake surface chop expected
Humidity: 67% · Barometer: 30.03 inHg
USGS water monitoring available for Grand Lake St. Marys.
Excellent for boating (98/100), from 4 available inputs. Supporting this: Wind 3 mph from the south. Gusts to 8 mph. Not available from a verified source for this lake: visibility and conditions, verified water access. Confidence is moderate (84%) because some inputs are unavailable or older than ideal.
Good for fishing (88/100), from 5 available inputs. Supporting this: Wind 3 mph from the south. 1% chance of precipitation. Not available from a verified source for this lake: pressure trend, water temperature. Confidence is moderate (74%) because some inputs are unavailable or older than ideal.
Excellent for kayaking (98/100), from 5 available inputs. Supporting this: Wind 3 mph from the south. Gusts to 8 mph. Confidence is high (90%).
Water temperature is not available from a verified source for this lake. No swimming score is shown without it. Supporting this: No active official alerts for this lake. 1% chance of precipitation. Not available from a verified source for this lake: water temperature.
| Time | Air Temp | Wind (mph) | Direction | Peak Gusts | Rain Chance | Sky & Conditions |
|---|---|---|---|---|---|---|
| 3 PM | 74°F | 3 mph | S | ⚡ 8 mph | 1% | Mostly Sunny |
| 4 PM | 75°F | 3 mph | S | ⚡ 8 mph | 1% | Mostly Sunny |
| 5 PM | 76°F | 3 mph | S | ⚡ 9 mph | 1% | Mostly Sunny |
| 6 PM | 75°F | 3 mph | SE | ⚡ 8 mph | 1% | Partly Cloudy |
| 7 PM | 74°F | 5 mph | SE | ⚡ 9 mph | 1% | Partly Cloudy |
| 8 PM | 70°F | 7 mph | SE | ⚡ 12 mph | 3% | Partly Cloudy |
| 9 PM | 66°F | 8 mph | SE | ⚡ 14 mph | 3% | Mostly Cloudy |
| 10 PM | 65°F | 9 mph | SE | ⚡ 16 mph | 3% | Mostly Cloudy |
| 11 PM | 64°F | 10 mph | SE | ⚡ 17 mph | 3% | Mostly Cloudy |
| 12 AM | 64°F | 10 mph | SE | ⚡ 17 mph | 2% | Mostly Cloudy |
| 1 AM | 63°F | 10 mph | SE | ⚡ 18 mph | 3% | Mostly Cloudy |
| 2 AM | 63°F | 10 mph | SE | ⚡ 18 mph | 1% | Mostly Cloudy |
| 3 AM | 62°F | 10 mph | SE | ⚡ 18 mph | 1% | Mostly Cloudy |
| 4 AM | 61°F | 10 mph | SE | ⚡ 17 mph | 1% | Mostly Cloudy |
| 5 AM | 60°F | 9 mph | SE | ⚡ 17 mph | 1% | Mostly Cloudy |
| 6 AM | 60°F | 10 mph | SE | ⚡ 17 mph | 1% | Mostly Cloudy |
| 7 AM | 59°F | 10 mph | SE | ⚡ 18 mph | 1% | Mostly Cloudy |
| 8 AM | 59°F | 12 mph | SE | ⚡ 20 mph | 1% | Mostly Cloudy |
| 9 AM | 61°F | 12 mph | SE | ⚡ 21 mph | 1% | Partly Sunny |
| 10 AM | 65°F | 13 mph | SE | ⚡ 21 mph | 1% | Mostly Cloudy |
| 11 AM | 68°F | 13 mph | SE | ⚡ 22 mph | 1% | Mostly Cloudy |
| 12 PM | 73°F | 14 mph | SE | ⚡ 22 mph | 1% | Partly Sunny |
| 1 PM | 75°F | 14 mph | SE | ⚡ 21 mph | 2% | Mostly Cloudy |
| 2 PM | 75°F | 14 mph | SE | ⚡ 23 mph | 1% | Partly Sunny |
Mirror-like to gentle rippled water. Optimal conditions for paddleboarding, kayaking, swimming, and beginner water skiing or wakeboarding.
Pleasant breeze with small wavelets. Great for sailing, pleasure cruising, pontoon boats, and trolling for trout and bass.
Moderate waves with whitecaps likely. Requires skilled boat handling; kayaks, canoes, and stand-up paddleboards should stay close to sheltered bays.
Steep waves, cold spray, and hazardous open water. Avoid small craft voyages. Always check official National Weather Service lake wind advisories.
Mostly sunny, with a high near 76. South wind around 3 mph.
Mostly cloudy, with a low around 59. Southeast wind 3 to 10 mph.
Mostly cloudy, with a high near 77. Southeast wind 10 to 14 mph, with gusts as high as 24 mph.
Rain showers likely between 9pm and 2am, then showers and thunderstorms. Mostly cloudy, with a low around 60. Southeast wind 15 to 20 mph. Chance of precipitation is 90%. New rainfall amounts between a quarter and half of an inch possible.
Rain showers likely before 2pm, then a chance of showers and thunderstorms. Mostly cloudy, with a high near 70. Northeast wind 3 to 16 mph, with gusts as high as 26 mph. Chance of precipitation is 70%. New rainfall amounts between a quarter and half of an inch possible.
A chance of rain showers before 8pm. Mostly cloudy, with a low around 59. Chance of precipitation is 30%. New rainfall amounts less than a tenth of an inch possible.
Mostly sunny, with a high near 80.
A chance of showers and thunderstorms after 2am. Partly cloudy, with a low around 65. Chance of precipitation is 30%.
A chance of showers and thunderstorms before 8am, then a slight chance of showers and thunderstorms between 8am and 2pm. Mostly sunny, with a high near 77. Chance of precipitation is 30%.
A slight chance of rain showers after 2am. Partly cloudy, with a low around 55.
A chance of rain showers. Mostly sunny, with a high near 69. Chance of precipitation is 30%.
A chance of rain showers. Mostly cloudy, with a low around 54. Chance of precipitation is 40%.
A chance of rain showers. Mostly cloudy, with a high near 69. Chance of precipitation is 40%.
A chance of rain showers. Mostly cloudy, with a low around 56.
Grand Lake St. Marys currently reports 57°F with wind velocity near 8 mph from the S. Atmospheric forecasts and 24-hour hour-by-hour wind timelines are updated hourly from the National Weather Service gridpoint matching the lake's coordinates.
At Grand Lake St. Marys and surrounding mountain valleys, diurnal heating of the surrounding terrain causes strong thermal pressure differentials known locally as afternoon breezes (such as the Washoe Zephyr at Lake Tahoe). Wind speeds typically peak between 1:00 PM and 5:00 PM before calming near sunset.
For stand-up paddleboarding (SUP), canoeing, and light kayaks, winds under 7 mph (light breeze) offer the safest, glassiest surface conditions. Between 8–14 mph, small wavelets develop, suitable for sailboats and powerboats. Winds exceeding 15 mph create steep whitecaps and rapid drift; winds over 21 mph warrant small craft warnings.
All weather and wind telemetry is fetched directly from the National Weather Service (NOAA - WFO ILN) high-resolution numerical point-forecast API. LakeRadar uses the official gridpoint for Grand Lake St. Marys without artificial smoothing or third-party estimates.
Yes. Live hydrological sensor readings, 30-day elevation histories, full-pool benchmarks, and USGS station provenance are available on our dedicated Grand Lake St. Marys Water Level & Temperature page.
View Grand Lake St. Marys Water Level & Temperature →