LOS ANGELES >> This might be the only state in the nation where a rainy day – complete with blinding sheets of water, shoe-sopping flooded intersections and chalk gray skies – puts people in a good mood.

And with good reason. The drenching rainstorm that settled here on Tuesday came as California wheezed its way into the fourth year of the worst drought in centuries. No matter that the storm was supposed to last only one day: The simple, if unfamiliar, act of grasping for umbrellas, turning on windshield wipers and jumping over puddles set off a combination of celebration and chaos.

"I just love it," said Ed Shaw, 64, a contractor in Los Angeles, who was enjoying what on the East Coast might be known as a snow day. "It’s at the top of list of the things we need."

In hard-hit Southern California, the storm was forecast to bring 2 to 6 inches of rain during the next 24 hours, a range that reflected the widely varying weather patterns in Los Angeles. If the forecast is accurate, this would be the biggest rainfall the region has experienced in two years. The average annual rainfall for downtown Los Angeles is 15 inches; last year, meteorologists measured just 3.6 inches.

"We are considering this the most significant storm of the year," said Mark Jackson, a meteorologist with the National Oceanic and Atmospheric Administration. "The last three years in downtown Los Angeles have been the driest three years on record."

The rain is not entirely good news. For one thing, unless this storm signals the beginning of a long and wet winter, a single day of rain will barely begin to address a drought that has bordered on biblical, drying up reservoirs, lakes and farmland.

The dry spell led to wildfires across the region, leaving miles of scorched hillsides dangerously prone for mudslides. Communities like Glendora, where the Colby Fire burned through 2 miles of hillsides in January, was put under a voluntary evacuation alert because of mudslides. About 800 homes were considered at risk, and 18,000 sandbags were handed out in the past 48 hours to guard against damage.

"It’s sort of a Dr. Jekyll and Mr. Hyde thing for us," said Chris Jeffers, the city manager of Glendora. "We are very happy for California. But these kinds of storms are concerning for us."

Ken Smolka, who has lived in Glendora for 30 years, said he was not worried.

"The city is incredibly well prepared this time," he said, adding, "the only people I know even thinking of, considering, evacuating – because, again, it is voluntary – are those that live at the highest point of the foothill mountains in some of the gated communities. But even then, I’ve heard them reiterate that it’s purely precautionary."

Some roads, including parts of the Pacific Coast Highway in Malibu, were shut down because of mudslides. Highways and roads across the region were snarled by traffic crashes as many here struggled to adjust to the unfamiliar challenge of driving on slick roads.

Or in some cases, did not adjust.

"For a state that doesn’t see a lot of water, it really surprises me how fast people drive in the rain," said Kajon Cermak, the traffic reporter for the radio station KCRW here. "Wouldn’t you think people would be nervous because they haven’t seen a lot of it? They fly through."

"Everybody is excited about it," she said. "But I don’t know why that would translate into risky, aggressive behavior."

The other concern was that the sight of rain would send the wrong signal to Californians, who have been urged to conserve water, with many communities imposing tough conservation measures.

"You will hear us say, ‘Conserve, conserve, conserve,’ every other sentence," said Mark W. Cowin, the director of the California Department of Water Resources. "If we could get one message out, it would be that nobody needs to be watering their landscapes this December. Go turn off your sprinklers."

But, said Cowin, who works out of Sacramento, it was hard not to see this as a good turn of events.

"I’m looking out the window right now at a December storm, something I didn’t get to do last year, so I’m pretty happy," he said. "This looks like a prolonged event, the kind of event we need. But we need these kind of storms to keep coming through December and January."

© 2014 The New York Times Company