Mother Nature is so fickle. First, a frustrating drought forced mandatory rationing in the South Bay. Now, more than half the area's reservoirs are overflowing -- a deluge that will provide residents with more than enough water even as much of it goes down the proverbial drain.

This week's storms, highlighted by Thursday's tempest that battered Northern California and proved to be the most powerful in 17 months, has pushed virtually every part of the Bay Area to well above normal rainfall totals for the season.

Even San Jose managed to soak up enough water to push this season's total rainfall to just shy of average, or even normal, depending on who's keeping score.

The National Weather Service pegs this year's San Jose rainfall at about a half-inch shy of average, while Golden Gate forecasters and the water district put it right at average. The Peninsula is at about 112 percent of average, with Santa Cruz at 123 percent of normal.

By Friday afternoon, six of the Santa Clara Valley Water District's 11 reservoirs had reached their limit. The Lexington, Uvas, Chesbro and Vasona reservoirs in south Santa Clara County were spilling over like an overfilled bathtub about five feet below their dams, while officials drained the Almaden and Coyote reservoirs because they had reached a limit considered safe. Any higher levels would make the reservoirs unsafe in the event of an earthquake.

Combined, those six reservoirs hold 16.6 billion gallons of water, yet more liquid had to be drained to the San Francisco Bay. Some of the reservoirs had spilled a few years ago, but Lexington had not reached its capacity since 2006.

That's when Todd Owens began commuting from San Jose to Santa Cruz, and ever since he's been watching Lexington Reservoir with a keen eye while driving down Highway 17.

"I kept watching it getting fuller and fuller" last week, Owens said. Then, on Thursday, "lo and behold, it was going over the top. It was actually kind of exciting for me because I've been watching it for so long and never seen it go over. Then (Friday) morning, it was even higher." He said drivers were pulling off the highway to watch the spectacle.

The spills came because Mother Nature saved her best for last this rainy season. In the past week, San Jose was doused with 3.76 inches of rain -- or 28 percent of the season's rainfall. The storm also hit Santa Cruz with 5.3 inches and the Peninsula with 3.87 inches, according to the National Weather Service.

Golden Gate Weather Services said Thursday's rainfall and wind gusts combined for the nastiest 24-hour stretch in the South Bay since October 2009.

And it's not over yet. Forecasters expected another half-inch of rain in the South Bay -- about the same amount that fell Wednesday -- starting Friday night and into Saturday afternoon. There could also be some sprinkles Sunday night.

"Looks like, after that, we'll begin to dry up, and temps will warm up nicely," National Weather Service forecaster Chris Stumpf said.

While some residents call it an annoyance, others figure the rain will provide water to drink, use around the house and landscape with for months to come.

"It's a boon, actually, this rain has been a boon," water district spokeswoman Meenakshi Ganjoo said. "We've had a dry spell for the past three years."

She noted residents had to reduce their water consumption by 15 percent through September because of a drought.

The storm was a long time coming for San Jose, which escaped much of winter's wrath because the winds gusting from the Santa Cruz Mountains had mostly moved away from the South Bay -- putting San Jose in a "rain shadow," meteorologist Jan Null said.

But other areas have had it much wetter. In the Sierras, record snowfall is turning spring into ski season all over again. Portions of routes 20 and 89 remained closed while chain controls and a temporary ban on big rigs were in effect for Interstate 80.

South of the Bay Area, on the coast, Highway 1 was closed for 49 miles south of Monterey.

But by Friday afternoon, all major Bay Area roads had been re-opened, the California Highway Patrol said.

Contact Mike Rosenberg at 408-920-5705.