The dreaded D-word – "drought" – is back on the tongues of many Californians now that a dry December has crawled into a dry January.

A dry December is not that unusual. But a dry January – well along into winter and usually the state's wettest month – is another matter.

"What is unusual is that it just hangs on and on and on," said Maury Roos, chief hydrologist at the California Department of Water Resources, noting it will be hard to recover from the missed January storms.

"It's not impossible, but it's quite unlikely we'll make it back to normal before the end of the season," Roos said.

Sacramento has had no rain since Dec. 15, and only a trace on that day: 0.07 inches.

Lake Tahoe – so dependent on snowfall for its winter economy – has fared just as badly. South Lake Tahoe has seen no measurable precipitation since Nov. 20, according to National Weather Service data.

"We've hit that point where it is actually starting to hurt morale and business," said Gary Bell, owner of Sierra Ski and Cycle Works in South Lake Tahoe. "We're starting to sacrifice piles of skis, wash our cars and anything we can do. It's the subject of discussion for everybody."

The Northern Sierra Nevada, a region critical to statewide water supplies, experienced its third driest December since record keeping began in 1920. Throughout the Sierra Nevada, the total snowpack as of Tuesday was 14 percent of normal.

Last week, the National Drought Mitigation Center, based in Nebraska, officially charted Northern California into "moderate" drought conditions, based in part on rainfall and soil moisture conditions.

State water leaders have not declared a drought – most reservoirs still hold above-average water supplies, thanks to the bounty of last winter. But they're definitely concerned.

Dry conditions are hanging on because California, unlike last winter, is experiencing the more typical effects of a La Niña, said Bill Patzert, a climatologist at NASA's Jet Propulsion Laboratory in Pasadena.

La Niña occurs when the waters of the equatorial Pacific Ocean enter a cool cycle – the opposite of El Niño. This typically drives the jet stream north of California, often diverting storms around the central state.

This didn't happen last winter – also La Niña-influenced – thanks to the compounding effect of another phenomenon: a negative Arctic oscillation. The negative oscillation pressed cold Arctic air farther south into the northern states, driving cold storms across California despite La Niña's influence.

That ended a three-year drought that had thrown the state into crisis mode, putting fish species and many crops in jeopardy amid competition for limited water supplies.

Will it prove to be just a respite from a much longer drought?

"At this point, we're in wait-and-see mode," said Jeanine Jones, Water Resources drought manager. "The wild card out there is we can't predict when we would get one of these major storms that would make all the difference."

This winter the Arctic oscillation has been positive, meaning that Arctic air is staying north, allowing La Niña to play out in a more typical fashion.

The Arctic oscillation usually fluctuates rapidly, changing phase in a matter of weeks. But this winter, it has stayed almost uniformly positive since September, Patzert said. This has allowed a "blocking ridge" of high pressure to linger over the West Coast for months, diverting storms to the north.

"Last year, it was a superhighway of storms down the spine of the Sierra, and we couldn't shovel fast enough," Patzert said. "But this year, essentially, the fence is up … and the jet stream has really stayed out of California."

Some California businesses are already sweating.

Livestock grazing, for instance, is largely dependent on rainfall to grow forage for cattle and sheep, and to fill stock ponds the animals need for drinking water.

Josh Davy, a livestock and range farm adviser with the University of California Cooperative Extension, said many livestock owners are in a waiting game. They're hoping for rain but are also making plans to buy supplemental feed in case it doesn't.

Another option for some, he said, is to begin selling off animals early to reduce herd size, thereby ensuring grazing lands can sustain the animals they keep.

"People are right on the teetering edge," said Davy, who serves Colusa, Glenn and Tehama counties. "We're going to have a lot of grass start dying here if we don't start getting some kind rains."

Some stone fruit and nut crops are also at risk. With these crops, such as almonds and peaches, root growth precedes bud growth. Without soil moisture, the roots don't grow, and then the trees don't bud out.

That means less fruit production, said Roger Duncan, a fruit tree advisor at the Cooperative Extension office in Stanislaus County.

Recognizing this risk, the Turlock and Modesto irrigation districts this week began preparing to deliver irrigation water, an unusual event for early January when rains normally provide all the moisture trees need.

This will help many farmers, but it also means they have to spend extra money buying water. Others will be able to rely on their own wells, but this comes at the cost of running pumps.

"They're starting to get concerned," said Duncan. "There is no such thing as normal. But I don't remember it being quite like this. We really could use the rain."

Fortunately, hints of a change are on the horizon.

In long-range forecasts released Tuesday, the National Weather Service predicted increased odds for above-normal rainfall from about San Luis Obispo north for the week starting Monday.

Accuweather has a similar prediction in its long-range forecast.

"If that's the start of a real winter, we'll be pretty happy," said Bell, the South Lake Tahoe ski and bike shop owner. "It'll work out."

© Copyright The Sacramento Bee. All rights reserved.

Call The Bee's Matt Weiser, (916) 321-1264. Follow him on Twitter @matt_weiser.

• Read more articles by Matt Weiser