Countless numbers of visitors ask this question every year. Such an event is a very rare occurrence which may happen only once in a lifetime. The last winter Crater Lake "froze over" was in 1949, when an icy layer completely covered it for over two months. Prior to 1949, the only other time this was reported to have happened was for four days during February, 1924.

Like most large bodies of water, Crater Lake is a heat reservoir where temperatures do not fluctuate greatly except near the surface. Below about 200 feet, water temperature remains at a perpetual 38 degrees Fahrenheit. When surface water is cooled by frigid air, it becomes denser and sinks, forcing up less dense warmer water. This usually prevents ice formation, but in 1949 the upper 200 feet of water cooled down to 32 degrees and the surface water even lower.

On March 14, 1949, two park rangers set out to investigate this unusual event. Using a predetermined route, they walked to Wizard Island. They descended into the caldera from Rim Village and found the ice thickness to be about 12 inches when they reached the shoreline. The ice layer was reduced to two inches at a spot where the lake is 1000 feet deep. At this point, the pair discovered watery slush filling their tracks, so they made a hasty advance to the island.

Since retracing their steps was out of the question, the two rangers decided to take the shortest route across the lake and go back along the shore. They crossed Skell Channel, where the ice had formed up to four feet thick, with no difficulties; but their most difficult hurdle still lay ahead. That was the 900 foot ascent back to Rim Village. This was made in snow averaging 150 inches deep at an angle of approximately 45 degrees. With perseverance and little more than luck, both of them returned that afternoon with their observations.

Crater Lake remained a giant expanse of white until almost mid May of 1949. Since then, the closest it has come to a repeat performance was during April 1983 when ice covered approximately 95 percent of the lake. We have not had such a "hard" winter since, but this could be one of those years....

Ecology of Crater Lake