Like every autumn, October is bringing cooler weather, changing leaves and pumpkins to fields across California.

But unlike the past five years, when a historic drought gripped the state, there’s something new across the landscape: full reservoirs.

From a water supply standpoint, California is heading into this winter’s rainy season in much better shape than any year since 2011. San Luis Reservoir, the massive inland sea between Gilroy and Los Banos that provides key supplies for Central Valley farmers and cities from San Jose to San Diego, is 86 percent full. A year ago it was only a quarter full.

Drenching storms last winter that prompted Gov. Jerry Brown to declare an end to California’s drought in April delivered enough water to raise the level by 121 feet at San Luis, which is nine miles long and the state’s fifth largest reservoir.

“I’m feeling a lot better this year than in years past,” said Grant Davis, director of the state Department of Water Resources in Sacramento.

Similar conditions exist around most parts of California. Los Vaqueros Reservoir, the biggest in Contra Costa County, is 94 percent full. All seven of the East Bay Municipal Utility District’s reservoirs are 83 percent full. Loch Lomond, the main reservoir in Santa Cruz County, is 93 percent full. And statewide, the 45 large reservoirs that form the backbone of California’s water storage are 120 percent of average for this time of year.

The 10 reservoirs operated by the Santa Clara Valley Water District are 45 percent full, largely because the district has been using them to steadily recharge its groundwater — the reason many of them were built.

All that carryover water means that even if this winter isn’t particularly wet, the chances of water restrictions next summer are low.

“Our reservoirs filled. We’re set up to have a couple of years worth of supply. So we’re not expecting to have shortages this summer,” said Andrea Pook, a spokeswoman for the East Bay Municipal Utility District, which serves 1.4 million people in Alameda and Contra Costa counties.

The question that keeps coming up again and again is: “How much will it rain this winter?”

Unfortunately, nobody knows.

Modern weather forecasting technology — with satellites, supercomputers, radar and temperature sensors spanning the globe — can only predict weather with any accuracy within a week to 10 days.

“I wish I had a crystal ball,” said Charles Bell, a forecaster with the National Weather Service in Monterey.

Short-term weather forecasts are markedly different than long-term climate trends.

Long-term climate patterns are easy to measure. The Earth continues to steadily warm — the 10 hottest years since 1880 all have occurred since 1998, for example, and the past three years have been the three hottest — as do the oceans. The warming water causes sea levels to continue to rise.

Computer models at NASA, NOAA, the Lawrence Berkeley National Laboratory and other scientific agencies can plug in the current rates of warming, sea level rise, carbon dioxide concentrations in the atmosphere and other factors to make general predictions about what the world will look like in 10 or 20 or 50 years if the trends continue.

If countries emit more heat-trapping gases, the global temperature goes up. If they emit fewer, it rises more slowly.

But forecasting the weather for a specific day in a specific place is much more difficult. Attempts to do so months ahead of time have regularly fallen flat. The Old Farmer’s Almanac last year predicted a dry year for California. It was, of course, wrong. This year it’s predicting a wet winter.

The National Oceanic and Atmospheric Administration’s long-range seasonal outlook last year predicted equal chances of a wetter-than-average, drier-than-average, or average rainfall season for most of California. It was wrong. The winter was much wetter than normal. And the agency is sticking with a similarly neutral prediction for this upcoming winter.

“If you look at the last two years, they have pretty much been 180 degrees out of sync,” said Jan Null, a meteorologist with Golden Gate Weather Services in Saratoga.

Null, a former forecaster with the National Weather Service, notes that forecasts are made by looking at everything from temperature patterns to barometric pressure to storm systems that form thousands of miles away in the Pacific Ocean. There are literally millions of variables, changing by the minute, so the closer a forecast is to the date desired, the more accurate it is.

Advances in technology are slowly helping.

“We’ve improved about one day per decade,” Null said. “When I started in the 1970s, we could get an accurate forecast about three days out. Now it’s seven days.”

Hydrologists measure years from Oct. 1 to Sept. 30. One thing is clear about the year that ended Saturday. In California, it was a near-perfect system of storms to end a big drought.

Some experts had said there was no way a drought as deep as California’s could end in one year — wrong again.

But a series of more than 40 soaking “atmospheric river” storms hit — and hit hard. They were spread out over many months and located mostly in the north, where the state’s biggest reservoirs were located. Eight key weather stations, from Mount Shasta to Lake Tahoe, received more rain last winter than any year since 1895, when modern recordkeeping began. And overall the state had the second-most runoff of any rain year except 1982-83, when massive El Nino storms caused widespread flooding.

The storms caused $100 million in flood damage to San Jose homes along Coyote Creek and shattered the spillway at Oroville Dam in Butte County, the nation’s tallest dam. The spillway remains under repair, and Oroville is the only big reservoir in Northern California with significantly less water in storage now than normal — a deliberate move by state water managers to improve safety while hundreds of construction workers rush to fix the spillway by Nov. 1.

Davis said the Department of Water Resources is working hard to improve the state’s ability to forecast atmospheric river storms, also known as “Pineapple Express” storms, which could help to better prepare for flood emergencies and help water officials better manage reservoir levels. His department is spending $19 million from the Proposition 84 water bond, approved by voters in 2006, to set up a system of more accurate radar to get a better sense of the size and scale of atmospheric rivers before they arrive.

The first new radar stations went in last month at the Santa Clara Valley Water District, where winter storms helped recharge depleted groundwater aquifers back to levels not seen since before the drought.

“On the heels of four or five years of drought, followed by the year that we just had,” Davis said, “that tells me we have to be prepared for just about anything.”