A winter storm dumped 13.5 billion gallons of water in Lake Tahoe over the weekend, along with 36 inches of snow at one Sierra Nevada ski resort and more than 10 inches of rain in some parts of the Bay Area. But is the drought over? No.

The National Weather Service says another two months of regular winter storms are needed to get the snowpack and reservoirs back to what was normal for this time of year. Unfortunately, "normal" may have already changed to a hotter and drier California—the way it was 500 years ago.

By looking at the width of tree rings in the Sierra Nevada, scientists know that California had an especially long and terrible drought 500 years ago. If this year remains dry, this current drought will be just as severe.

The high estimate of California's pre-European population is 705,000 people. Today, there are 38,400,000 Californians.

The weather system that arrived on Friday was the first big storm to reach Northern California since December of 2012.

"There's still 40% of the wet season left," California chief hydrologist Maury Roos told the Fresno Bee. "And we're seeing some good signs of a change in the weather pattern. But it is pretty grim at this point."

[Photo via AP.]