🌤 Weather at Grand Lake St Marys State Park by season
| Spring | Summer | Fall | Winter |
|---|---|---|---|
| 30–73 °F | 60–84 °F | 33–77 °F | 19–38 °F |
Each range runs from the coldest monthly average low to the warmest monthly average high in that season (1991-2020 climate normals), measured at Celina 3 NE, 3 mi away, elevation 866 ft. Conditions at the park can differ from the station, especially where elevation differs — check a forecast before you go.
Activities
Guests at the park can engage in a myriad of outdoor recreational pursuits during their time there. Outlined below is a brief overview of some of the main activities you can do whilst visiting Grand Lake St Marys State Park.
Water Activities at Grand Lake St Marys State Park
With there being no limit on horsepower, boating is a very popular pastime at Grand Lake. Many people come to the park to whizz around the lake on their private vessel. Although they are encouraged to do this well away from the shore. The likes of kayaking, canoeing, SUP and boating are also regularly practiced, while water skiers can get their adrenaline-fueled kicks too. All up there are nine launch ramps dotted around the lake, which makes access to the water quite straightforward. Swimming is another much loved activity, particularly during the warmer months of summer. As the water is less than seven feet in depth you should not get into too much difficulty if you are sensible when going for a dip. Overall there are four swimming beaches around the lake you can choose to swim at. Some of these are lifeguarded during the weekends and holidays.
Fishing at Grand Lake St Marys State Park
Anglers from all over Ohio and the neighboring states are drawn to the park for its excellent fishing opportunities. Many of which choose to venture out at sunrise to take in the magnificent hues and cast a line. You may need a license to fish at the lake, so it is best to check with the park on the current rules and regulations. However, once you have been given the green light, you can expect to snare a host of species including bass, bluegill, crappie and yellow perch. For those who want to fish but forgot to bring their equipment, you can rent rods and reels from the park’s camp store.
Biking at Grand Lake St Marys State Park
If you are into biking there are several roads that will take you to various points within the park. Collectively they showcase the park’s picturesque landscape and most notable points of interest including the nature centers, cedar cabins, boating ramps and of course various look outs around the lake. Bikes can be hired from the camp store who will also be able to tell you the best areas to enjoy the stunning sunrise and sunsets.
Birding & Wildlife Watching at Grand Lake St Marys State Park
If you are into birding or wildlife watching the park provides plenty of opportunities to enjoy these activities. Through its varying terrain of wetlands, woodlands and prairie ecosystems you will be able to see several breeds of birds. This includes many who live in the park all year round, as well as other who stop off during their annual migration. Depending on the time of year you visit you can expect to see grebes, ducks, swans, geese, loons, egrets and herons. The likes of bald eagles, ospreys and cormorants and ospreys are regularly viewed too. At ground level, look out for mink, beavers, white tailed deer, fox squirrels and raccoons who can often be seen throughout the park.
Pets at Grand Lake St Marys State Park
Pets are welcome to join you at Grand Lake St Marys State Park however there are certain restrictions in relation to their presence at the park. For example, dogs must be kept on a hand-held leash of no more than six feet and well behaved at all times. They also are not permitted in the cabins and any of their defecation must be cleaned up and disposed of properly. While pets are prohibited from joining you in the cabins, there is a dog park available for them to use. They are also allowed in most other areas of the park.
Camping at Grand Lake St Marys State Park
For those who require a place to stay whilst visiting the park its large campground provides plenty of accommodation options. Overall there are 217 campsites within the complex, most of which are situated close to the water. Of these, 33 sites come with full hookups for RVs and trailers, while a further 115 have connections for electricity. The remainder do not provide access to water or electricity and are best set up for self-sufficient campers. Generally the campground area is flat and flanked by trees that provide good shade. It also features seven cabins you can hire, as well as a range of amenities including flush toilets, hot showers, a dump station, individual grills, fire rings and picnic tables.
Park Location
Grand Lake St Marys State Park 834 Edgewater Drive St Marys, OH 45885 Phone: 419.394.3611 Website Reservations
Map
Video
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Explore More Ohio State Parks
Grand Lake St Marys State Park is one of many outstanding state parks in Ohio. Discover more parks in our Best State Parks in Ohio guide, or use our Park Finder to search by activity, location, or features.
Nearby state parks: If you have extra time, Lake Loramie State Park is a short drive away, and Lake Loramie State Park is a short drive away.
🐾 Dogs & Pets at Grand Lake St Marys State Park
- Pets allowed? statewide rule
- Pets are allowed in Ohio state parks and in all state park campgrounds (maximum two pets per campsite) but must be leashed in public areas.
- Leash rule statewide rule
- Leash not to exceed 6 feet in length, in hand and under control
- Beaches & swim areas statewide rule
- No pets allowed at swimming beaches; some parks have designated dog swim areas and dog parks
- Cabins & lodging statewide rule
- Pet-friendly cabins available at select parks (Buck Creek, Cowan, Dillon, Lake Hope, Mohican, Pike Lake, Pymatuning); maximum two pets per cabin; $10 added fee
- Pet fees statewide rule
- $10 added fee for pet-friendly cabins (charged whether pets come along or not); no pet fee for day use or camping
- Statewide exceptions statewide rule
- Designated leash-free dog exercise areas exist at some parks; no bathing of pets in campground shower houses
Are dogs allowed at Grand Lake St Marys State Park?
Pets are allowed in Ohio state parks and in all state park campgrounds (maximum two pets per campsite) but must be leashed in public areas. Individual parks can post stricter rules — check signage on arrival.
Rules verified July 2026 via ohiodnr.gov. More: Ohio state parks guide · Dog rules in all 50 states compared
Park Location
Plan your gear for Grand Lake St Marys State Park
From our editorial guides, matched to this park’s activities:
