If you hate tornadoes, you have to love drought.

That sounds a bit strange, but consider this: When there's a drought, you have fewer thunderstorms and, therefore, scant tornadoes.

Drought could have a bearing on this year's tornado season, says Ken Dewey, professor of applied climate science at the University of Nebraska-Lincoln.

Climate records show that between 2002 and 2008, when most of the state was in the grip of a drought, the number of tornadoes was below normal for that time period, Dewey said.

Since 1971, the state has averaged about 48 tornadoes a year.

"In 2006, at the height of the drought, there were no tornadoes in eastern Nebraska and 22 in the entire state," he said.

The only exception was 2004, when Nebraska had 110 tornadoes, including the two-mile-wide twister that almost leveled Hallam on May 22.

Seventy-six tornadoes were recorded in Nebraska during May 2004 - 60 of them on May 22 alone, said Dewey, who noted that the week of May 22 was very wet.

Nebraska has just come out of a long-term drought, Dewey said, but could be entering another one.

Most of the state is currently drier than normal, with precipitation ranging from 1 inch to 3 inches below normal year-to-date, according to the High Plains Regional Climate Center.

Lincoln had 1.73 inches of precipitation as of Wednesday, the National Weather Service said. Normal by that date is 4.77 inches.

But Dewey said it's too early to predict what will happen this year.

"If it stays dry, we won't have more storms," he said. "We had an early start, but that doesn't tell us anything about the rest of year."

NWS meteorologist Barbara Mayes is part of a research group from nine northern and southern Plains states that has studied the effect of La Niñas - unusually cold water temperatures in the Equatorial Pacific - on tornado seasons.

"Basically, we found when a La Niña is present, the potential for a more active tornado season increases," Mayes said.

Mayes said a strong La Niña may have helped produce the larger number of tornadoes that touched down in Nebraska last year.

Now, the La Niña effect is weaker, so the impact on tornadoes remains uncertain, Mayes said.

The "clash of the seasons," or the contrast of cold and hot air, also will play an important role, Dewey said.

"Severe weather has to have just the right ingredients for tornadoes to form," Dewey said. "You need moisture or energy contrast."

Reach Algis J. Laukaitis at (402) 473-7243 or alaukaitis@journalstar.com.