🌤 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.
Considering how majestic the views of the sunrises and sunsets are at Grand Lake St Marys State Park it is surprising that it still remains somewhat of a hidden gem.
Set around the shimmering waters of the picturesque 13,500-acre Grand Lake, this Ohio state park is a haven for those who enjoy boating, fishing, water sports and swimming.
It is also a must visit destination for photographers, wildlife and nature lovers, while cyclists can explore the park through several scenic miles of road.
Covering a distance of 591 acres, the park is a popular day trip destination and weekend getaway from Columbus and Dayton.
However, for those who choose to stay for a night or two, the modern, onsite campground offers 217 campsites. Most of which come with either full or partial hookups for your rig.
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
At Grand Lake St Marys State Park, pets are permitted in most areas, but not in the cabins or on the swimming beaches. Two fenced dog parks let your dog run without a leash: the Fur-Ever Friends Dog Park on the East Bank and the Celina Rotary Dog Park on the West Bank (Grand Lake St Marys park page). In the campground, pets are permitted on all sites except in and around the cabins, not in the camper cabins, and registered campers have their own dog park (campground page).
Ohio State Parks rules apply: keep your pet on a hand-held leash no longer than 6 feet and under control at all times, except inside a designated dog exercise area, and carry proof of its rabies vaccination (Ohio DNR state park rules, as of October 2026).
In the campground, up to two pets are allowed per site. Don’t leave your dog or cat unattended (on your own site it may be tethered on a securely anchored lead), keep it out of enclosed camping structures and off the camp beach, pick up after it, and make sure it wears a collar or tag with your name and address (Ohio Administrative Code 1501:46-9-10).
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
Map
Video
Here is a video review of Grand Lake St Marys State Park:
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 parks: If you have extra time, 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
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