As parts of the U.S. start to climb out of drought, other areas may head into one, according to historical weather patterns.

Fall rains delivered a slight re-prieve to some drought-stricken areas of the U.S., bringing 80% of the Corn Belt up to full moisture, says Elwynn Taylor, ag meteorologist at Iowa State University.

Most of the Midwest, except for the upper Mississippi Valley, has had a wetter-than-normal winter through early February. Indiana and Illinois fields flooded in early January, with additional flooding in early February in the central and eastern Corn Belt. Many areas west of the Mississippi River were drier than normal in January. But some areas had good snowfall. Cedar Rapids, IA, for example, had 47.6" of snow through Feb. 7.

“That's the only favorable thing we've got,” Taylor says of the Mid-west. “The rest starts to look like the ‘perfect storm’ for conditions to have drought.”

A historical average lapse of 19 years between major droughts — and the last drought in 1988 — indicates that the Corn Belt is due for one, Taylor says. The longest gap has been 23 years.

Another historical indication that drought is in the region's near future: Of the past 17 major droughts, 16 followed droughts in South Carolina. Last summer, that state suffered yet another.

Midwestern droughts are determined more by temperature than by precipitation, he points out.

In 1994, for example, rains were scant but temperatures were cooler than normal, with record yields in the Corn Belt. The next year brought more rain but excessively high temperatures, resulting in near-drought conditions.

In other parts of the country, La Niña, a weather pattern caused by air pressure changes between the western and eastern tropical Pacific, is playing with temperatures and precipitation.

“The southern tier of the country typically sees drier seasons” during a La Niña, says Brian Fuchs, climatologist for the National Drought Mitigation Center at the University of Nebraska-Lincoln. “The Pacific Northwest and Ohio River Valley get above-normal precipitation.”

Those areas saw such effects in January — as well as abrupt and extreme temperature changes. The Feb. 7 National Weather Service forecast indicates a moderate-to-strong La Niña through the winter with a continuation of a weaker La Niña from April through June, which means continued drought for South-ern regions.

Other parts of the country are pulling out of droughts they've been in for several years, adds USDA staff mete-orologist Brad Rippey while examining U.S. Drought Monitor maps.

• In the Pacific Northwest, recent storms dropped heavy snow in northwestern winter grain areas. Montana, southeastern Oregon and southern Idaho are the only states in that region showing signs of drought. Much of the remainder of the West has been in a fairly wet pattern since late November or early December, which is beneficial for pastures and rangeland. Still, the Drought Monitor shows lingering long-term hydrological drought — a prolonged period of low precipitation and low water levels.

• The Southwest received heavier-than-normal precipitation the past two months, which is fairly unusual for a moderately strong La Niña. But long-term drought is predicted in parts of the region, particularly in southern California. Southern Texas is dry and pastures need moisture.

• In the northern and southern High Plains, wet conditions last spring and summer helped build soil moisture. “Last year was one of the best years in the High Plains for wheat and pasture,” Rippey says. Yet there's a long way to go, he adds.

  “With short-term dryness this winter,” says Fuchs, “there's concern about just how dry those soils are. It's a coin flip for forage production.”

• The Northeast's near-normal and above-normal precipitations in recent months have erased vestiges of drought.

• The Southeast has had short-term wetness in areas, aiding pastures and winter grains after a long-term drought.

“However, many Southeastern rivers and lakes have been slow to respond to the rainfall, meaning that the soil profile continues to moisten but that little runoff is occurring,” Rippey says.

“It's going to take quite a bit of precipitation to affect it,” Fuchs adds. In 2007, the area was 20-30“ below normal precipitation, with a late freeze in April.

Florida remains very dry, and pastures are in rough shape, Rippey says.

“With La Niña conditions, I anticipate it will be dry,” Fuchs says. “Come spring, I can't see that spring grazing will improve much.”