“In a three-month period, there’s a lot of noise in that signal,” said Jonathan Erdman, senior digital meteorologist for IBM's weather.com. “It’s not just one thing. It’s a handful of things.”

The major driver of winter weather is La Niña. This is the name for the phenomenon when cold water in the Equatorial Pacific pushes up the jet stream. As a result, the northern half of the United States experiences a colder than normal winter, while the South experiences one that’s warmer than average.

“Those temperature patterns wind up influencing the atmosphere over the United States, particularly so during the winter months,” Erdman said.

A Season of Shivers

But wait. Last year was also a La Niña year. Yet southern states suffered through a record cold snap. That’s because more than one factor affects the weather, Erdman said. Another major factor is blocking high pressure over the Arctic. That forces cold air downward, which is what happened in February.

Right now, Erdman said conditions are right for both events to recur. The developing La Niña is part of the reason for this year’s warmer-than-usual fall. This means cold weather from the Pacific Northwest to the west side of the Great Lakes. If blocking takes place, the cold weather will extend across the entire Great Lakes region and into the Northeast. Meanwhile, the Southwest and Gulf Coast should experience a warmer-than-average winter.

Erdman said the winter outlook will become clearer by mid-November. He expects temperatures to remain above average until then. Erdman said seasonal forecasts are difficult due to the many factors and the amount they change.

Weather patterns vary within regions and even within states, said Janice Stillman, editor of The Old Farmer’s Almanac. Still, her publication is predicting “a season of shivers.”

“It’ll be a winter like many people haven’t seen in a good, long time,” Stillman said.

The Old Farmer’s Almanac adds another factor to its forecast in sunspot activity. This is a result of magnetic patterns on the sun that last for about a decade. Right now, sunspots are fairly inactive, which adds to cooler temperatures.

There’s one more factor that complicates all these forecasts, and that’s climate change. Erdman said the biggest effect is summers growing longer, lingering into the fall. He uses the example of parts of North Dakota reaching 100°F this September, 12 days later than ever before. Climate change also tends to make winters wetter, with more sleet and less snow.

With all this uncertainty taken into account, here are the early forecasts for how different regions will fare this winter.

Pacific Northwest
After an unusually hot summer, residents in the Pacific Northwest should enjoy a mild winter, at least those along the Pacific Coast. The best news, according to AccuWeather, is early winter storms should put an end to wildfire season. A wet winter should help elevate the drought conditions in the region. East of the Cascades should be colder and drier than normal, The Old Farmer’s Almanac predicts.

Southwest
It’s been hot and dry in California this summer, and the forecast for the winter is the same. The state could see some relief later in the winter due to a weaker La Niña. The same goes for Nevada and Arizona, according to The Old Farmer’s Almanac. AccuWeather expects a mild start to the winter in Texas, but a drop in temperatures after the start of the year. Oklahoma and Arkansas should also prepare for colder winters.

Mountain States
For those who operate in ski areas, the most important weather forecast is how much snow to expect. The good news is these areas should receive plenty of snow to bring back skiers. Other than that, the region should experience a mild winter, according to The Old Farmer’s Almanac.

Midwest
This region can expect a cold winter. Stillman said this is especially true if cold weather drops down from Canada, since there’s little to stop it in this region.

Great Lakes
The Great Lakes region will experience a cold winter, but snow should hold off until January. That’s due to warmer than normal temperatures in the Great Lakes, AccuWeather predicts.

Northeast
This region should also expect a cold winter. Winters could last longer in New England, AccuWeather predicts, with some late season nor’easters.

Southeast
Cold is less an issue in this region than storms. The one area that can expect colder weather is the Carolinas, The Old Farmer’s Almanac predicts. These states experienced an unusually mild summer that several HVAC contractors said hampered their sales.