To many it is a singular fact that Lake Tahoe never freezes over in winter. This is owing to its great depth, possibly aided by the ruffling and consequent disturbance of its surface by the strong northeasterly winter winds. The vast body of water, with such tremendous depth, maintains too high a temperature to be affected by surface reductions in temperature. Experiments show that the temperature in summer on the surface is 68 degrees Fahr. At 100 feet 55 degrees; at 300 feet 46 degrees; at 1506 feet 39 degrees.
Twenty years ago the thermometer at Lake Tahoe registered 18 degrees F. below zero, and in 1910 it was 10 degrees F. below. Both these years Emerald Bay froze over. Perhaps the reason for this is found in the fact that the entrance to the bay is very shallow, and that this meager depth is subject to change in surface temperature, becoming warmer in summer and colder in winter. This narrow ridge once solidly frozen, the warmth of the larger body of water would have no effect upon the now-confined smaller body of Emerald Bay. Once a firm hold taken by the ice, it would slowly spread its fingers and aid in the reduction of the temperature beyond, first producing slush-ice, and then the more solid crystal ice, until the whole surface would be frozen solid.
An explanation of the non-freezing of the main Lake has been offered by several local “authorities” as owing to the presence of a number of hot springs either in the bed of the Lake or near enough to its shores materially to affect its temperature. But I know of few or no “facts” to justify such an explanation.
When I first visited Lake Tahoe over thirty years ago I was seriously and solemnly informed by several (who evidently believed their own assertions) that, owing to the great elevation of the Lake, the density of the water, etc., etc., it was impossible for any one to swim in Lake Tahoe. I was assured that several who had tried had had narrow escapes from drowning. While the utter absurdity of the statements was self-evident I decided I would give myself a practical demonstration. To be perfectly safe I purchased a clothes-line, then, hiring a row-boat, went as far away from shore as was desirable, undressed, tied one end of the rope around the seat, the other around my body, and—jumped in. I did not sink. Far from it. I was never more stimulated to swim in my life. My ten or fifteen feet dive took me into colder water than I had ever experienced before and I felt as if suddenly, and at one fell swoop, I were flayed alive. Gasping for breath I made for the boat, climbed in, and in the delicious glow that came with the reaction decided that it was quite as important to feel of the temperature of lake water before you leaped, as it was to render yourself safe from sinking by anchoring yourself to a clothesline.