Open Water Data

Volunteer Park - Flathead Lake

Lakeside, Montana, United States

  • Water Quality Status
    Passed tests Wed, Sep 3, 2025 at 4:33pm

Flathead Lake in northwest Montana is the largest natural freshwater lake west of the Mississippi; slightly larger than Lake Tahoe at 27.3 mi. long, 15.5 mi. wide, and max depth of 370.7 ft.

Well maintained park with short grass and beautiful landscaping surrounding 1 large pavilion with 8 picnic tables and 2 other smaller pavilions with 1-2 picnic tables each. The beach is sandy with small rocks. The swim area is roped off and has 2 docks with ladders to get into the lake and a swim out dock with 2 ladders. No concessions available so bring your own food and drink. Facility include a large indoor bathroom and changing room with flush toilets, 7 benches, 2 bike racks, 3 trash cans, and an outdoor water fountain.

As one of the cleanest in the world, Flathead Lake is perfect for OPEN WATER SWIMMING! No sharks, no jellyfish, and no lane lanes...just clear, clean, and crisp water!

Unless you like your water COLD, the effective swimming season is June through September. Average water temps in June are in the 60s, 70s in July and August, and then back down again in September.

Summer air temperatures average in the mid-70s to mid-80s.

Swim Guide shares the best information we have at the moment you ask for it. Always obey signs at the beach or advisories from official government agencies. Stay alert and check for other swimming hazards such as dangerous currents and tides. Please report your pollution concerns so Affiliates can help keep other beach-goers safe.

Beach conditions change constantly, and it is never wise to swim in open water up to 48-hours after a heavy rain. Please use caution!

The description above was copied from or heavily based on Swim Guide, with permission.

More Information