How cold is Lake Chelan?

Lake Chelan may shimmer like a tropical oasis under the Washington summer sun, but don’t be fooled by its dazzling blue color—this glacially carved lake is cold. With depths reaching nearly 1,500 feet, Lake Chelan is one of the coldest large lakes in the Pacific Northwest, especially below the surface. If you’re planning a swim, a boat ride, or just curious about the lake’s unique thermal behavior, here’s what you need to know about how cold Lake Chelan really is.

The Basics: Lake Chelan’s Temperature Profile

Lake Chelan is what limnologists call a deep, oligotrophic lake—it’s low in nutrients, extremely clear, and thermally layered. The temperature of its waters varies dramatically by season, depth, and location.

Surface Temperatures

Summer (June–August): The surface temperature can reach a pleasant 65°F to 70°F (18°C to 21°C), especially near the southern end around the city of Chelan.

Spring/Fall: In May and September, surface waters typically range from 50°F to 60°F (10°C to 15°C).

Winter (December–February): Surface temperatures can drop to mid-40s°F (around 7°C) but the lake never freezes, even during the coldest winters.

It Gets Colder As You Go Deeper

Lake Chelan has a remarkably stable deep water layer that stays cold year-round. This is especially true in the Lucerne Basin, the lake’s northern and deeper section.

◉ At depths below 300–400 feet, the water temperature rarely climbs above 45°F (7°C), regardless of the season.

◉ Near the bottom (~1,486 feet), temperatures hover around 39°F to 41°F (4°C to 5°C) all year long.

Because the lake is so deep and narrow, sunlight and wind can't easily mix the water column, so the deep zones remain icy cold even during summer heatwaves.

Thermal Stratification: Why It Stays Cold

Like many deep lakes, Lake Chelan experiences thermal stratification during warmer months:

◉ The upper layer (epilimnion) warms up with sunlight.

◉ The middle layer (metalimnion or thermocline) forms a sharp temperature gradient.

◉ The bottom layer (hypolimnion) remains cold and undisturbed.

Stratification typically starts in late spring, peaks in mid-summer, and breaks down in fall, when surface waters cool and mix with deeper layers again. This natural process helps the lake maintain its pristine clarity and cold-water fish habitat.

Swimmers Beware: Sudden Temperature Changes

Even if the surface feels swimmable, sudden drops in temperature are common just a few feet below. Swimmers who venture too far from shore may quickly find themselves in frigid water, especially in spring or early summer. Hypothermia can set in quickly if you're unprepared.

For casual swimming, the best spots are the shallower nearshore areas in the southern Wapato Basin, particularly near Chelan, Manson, and Don Morse Park, where the sun warms the water more effectively.

Why Cold Matters: Ecosystem and Recreation

Lake Chelan’s cold waters are crucial for its unique aquatic life. The lake supports cold-water fish species such as lake trout, kokanee salmon, and cutthroat trout, which thrive in the colder, deeper layers.

For recreation, the cold temps mean:

◉ Wetsuits are recommended for longer swims or water sports, especially in spring or in the upper lake near Stehekin.

◉ Scuba divers and open-water swimmers should be prepared for significant thermoclines and bring appropriate gear.

◉ Boaters and kayakers should be cautious of cold-water shock risk if capsized.

Quick Facts: Lake Chelan Water Temperature

Season	Surface Temp (Approx.)	Deep Water Temp
Summer	65–70°F (18–21°C)	39–45°F (4–7°C)
Spring	50–60°F (10–15°C)	~41°F (5°C)
Winter	40–45°F (4–7°C)	~39°F (4°C)
Fall	50–60°F (10–15°C)	~41°F (5°C)

Conclusion: Cold, Clear, and Captivating

Lake Chelan’s cold water is not just a defining feature—it’s part of what makes the lake so special. Carved by glaciers and fed by snowmelt, the lake holds onto its chill even during the hottest summer days. Whether you're swimming, boating, or fishing, understanding the lake’s temperature patterns helps you stay safe and appreciate the unique natural environment beneath the surface.

So how cold is Lake Chelan?

In short: refreshingly cool at the surface—bone-chillingly cold at the bottom.