The Glory Hole acts as flood mitigation for the the manmade lake, serving as a massive funnel once water levels reach about 440 feet. Last year, water levels at the spillway edged on the brink of activation for weeks, but never managed to spill over.

Parts of northern California could see up to a foot of rain, but Phoenix will remain dry and warmer than usual.

In what has become a much-anticipated sight, the morning glory spillway at Lake Berryessa is now active after this week's storms.

There’s really nothing like it. It’s a very odd-looking spillway that just disappears into the void. You almost have to see it.”