The La Nina that has driven the extreme weather since winter is over, but the lingering effects mean no summer for the Great Lakes, drought conditions expanding out of the southern Plains and flooding expanding into the Midwest from the Mississippi Valley.

The weather pattern that produced a wild winter for the Northeast and parts of the Midwest, then extreme flooding and devastating killer tornadoes this spring, is changing to one that may not be as volatile this summer.

However, given the national economic impacts of the tornadoes and floods this spring, all it would take is one hit by a major hurricane to stress the economy even more.

Senior Meteorologist Paul Pastelok, leader of the AccuWeather.com long-range forecasting team, said a change in the weather pattern means areas of the lower Mississippi Valley hit by flooding will have hot, drier weather this summer, which could help clear standing water and dry saturated ground.

“However, we will need to keep a careful eye on the tropics as late-season tropical storms could threaten the Gulf and/or East Coast states,” Pastelok said.

Midwest summer

The end of the La Nina pattern will threaten to make this area a region “without a summer,” Pastelok said. “Repeated intrusions of cool air from Canada along with showers and thunderstorms will keep temperatures below normal in many areas.

“Temperatures topping 90 degrees may be rare.”

The severe weather that has plagued the South this spring will shift northward.

Frequent bouts of thunderstorms could mean numerous instances of flooding, hail and wind damage, even tornadoes.

While we probably had the most extreme tornado activity of 2011 during April and May, the summer still has potential to bring a few moderate outbreaks of tornadoes.

Flooding may be the biggest concern this summer, as already-soggy ground can handle only so much heavy rain.