How cold is Crater Lake?

Crater Lake, renowned for its breathtaking blue waters and volcanic origins, is also one of the coldest lakes in the United States. Nestled within a collapsed volcano in southern Oregon, this deep alpine lake is fed solely by snow and rain, with no inflowing streams or rivers. Its elevation, depth, and geographic location all contribute to its consistently low temperatures.

In this article, we’ll explore just how cold Crater Lake is, how its temperature varies with depth and seasons, and what that means for swimmers, boaters, and the lake’s unique ecosystem.

Average Surface Temperatures

The surface temperature of Crater Lake can vary significantly depending on the time of year:

Summer (July–September): Surface temperatures can reach 50°F to 60°F (10°C to 15.5°C) during the warmest months. However, this is only the top few feet of water.

Spring and Fall: The surface quickly cools to the 40s°F (4–9°C).

Winter (November–May): The surface can drop to near freezing (32°F or 0°C), although the lake rarely freezes over completely due to its depth and thermal properties.

Even at its warmest, Crater Lake is still quite cold compared to typical swimming lakes.

Water Temperatures by Depth

Crater Lake is the deepest lake in the United States, plunging to a depth of 1,943 feet (592 meters). Its immense depth means that sunlight and warmth do not penetrate far beneath the surface. Below the upper layers, the water remains extremely cold year-round.

◉ At depths below 300 feet (90 meters), the temperature stays at a near-constant 38°F (3.3°C) throughout the year.

◉ Because Crater Lake doesn’t have rivers to circulate warmer or sediment-laden water, its deep layers remain undisturbed and frigid.

This cold stratification also preserves the lake’s exceptional water clarity and helps support its unique biological balance.

Does Crater Lake Freeze?

Despite its cold temperatures, Crater Lake rarely freezes over completely. This may seem surprising given its alpine setting and annual snowfall that can exceed 500 inches (1,270 cm).

Several factors prevent the lake from freezing:

Depth: The vast volume of water retains heat at lower levels, preventing complete freezing.

Thermal Inertia: The sheer size of the lake slows temperature changes.

Winds and Storms: Frequent winter storms keep the surface water churning, disrupting the calm conditions required for ice to form.

Historically, the last known time Crater Lake froze over was in 1949, and even then, the ice was thin and short-lived.

Is It Safe to Swim in Crater Lake?

Yes, swimming is allowed in Crater Lake—but it’s only permitted in one location: Cleetwood Cove, accessed via a steep, 1.1-mile trail on the north side of the lake. Even in summer, swimmers are greeted by icy waters that rarely rise above 60°F (15.5°C).

For most visitors, this quick dip is more of a refreshing plunge than a long swim. The cold shock is invigorating, but swimmers should be cautious, especially those sensitive to cold or with medical conditions.

The Role of Cold Water in Preserving the Lake

The consistently cold temperature of Crater Lake plays a vital role in its ecological and visual purity:

1. Limits Algae Growth: Cold temperatures slow the growth of algae, maintaining the lake’s legendary clarity and intense blue color.

2. Supports Cold-Water Species: Fish species like kokanee salmon and rainbow trout, which were introduced in the early 20th century, thrive in the lake’s cold, oxygen-rich waters.

3. Reduces Bacterial Activity: Lower temperatures mean slower decomposition and microbial activity, further helping water purity.

A Lake of Icy Beauty

Crater Lake’s chilly waters are part of what makes it so uniquely beautiful and well-preserved. While it may not be the place for a leisurely swim, its cold, clear depths create an environment unlike any other in North America. The lake’s ability to stay pure, deep blue, and biologically stable owes much to its low temperatures, high elevation, and isolation from external water sources.

Final Thoughts

So, how cold is Crater Lake? The simple answer is: cold enough to keep you alert, clear your head, and remind you that you're standing before one of nature’s most pristine wonders. Whether you dip your toes in at Cleetwood Cove or simply admire its icy surface from the rim, Crater Lake’s cold waters are central to its enduring magic.