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Fox News Weather Center

WATCH: Oregon Lake Mysteriously Vanishes Every Spring

At Willamette National Forest in Oregon, there's a lake that only fully exists eight months out of the year.

From October to May, rain and snow that bears down on the Cascade Mountains will run off and form a lake in western Oregon. However, the same area sits empty from May to September.

Known as a lava tube, a hole sits in the northern floor of the lake and the lake will drain down the opening. Formed anywhere from 3,000 to 7,000 years ago, lava at one point snaked through the earth and formed a subway tunnel-like tube.

The hot lava hit cold air or rocks, hardening the outer layer and forming the passage, Jude McCugh, Willamette National Forest spokesperson, said.

As rain and snow collects during the wetter months in the western United States, the lake will gradually increase in depth after the precipitation exceeds the open space for water to sit below the surface, siphoned off down the hole.

As precipitation rates drop during drier months, the lake will disappear as water streams down the lava tube.

Though officials are not entirely sure where the water ends up, it does resurface years later.

Water from the high Cascades will move through the pores and cracks of the rocks, reemerging about seven to 10 years later, McCugh said.