WEST LAFAYETTE — Hoosiers should keep their umbrellas and flashlights handy because the thunderstorms that have marked spring, especially early June, likely will continue until the end of July.
La Niña’s control of the weather pattern will continue to make Indiana's normally severe storm season more intense and generate storms more frequently than average, said Dev Niyogi, state climatologist and an assistant professor of agronomy and earth and atmospheric sciences at Purdue University. La Niña is a name given to the interaction of the atmosphere with cooler than normal sea surface temperatures in the tropical Pacific. This impacts global weather patterns.

“Whenever we are in a La Niña pattern, there is increased propensity for severe weather over Indiana during spring and summer with increased likelihood for thunderstorms and rain,” Niyogi said. “We are nearing the end of the La Niña cycle, which started last year, but the sea surface temperatures are still about one-half a degree cooler than normal.”
The cool ocean surface temperature and recent precipitation deluge tell climatologists that La Niña still has some punches to throw, he said.
La Niña could be the major reason for the weather pattern responsible for 9.85 inches of rain in Gosport in Morgan County on June 7. Edinburgh, Ind., has the rainfall record for the week of June 2-8 with 17.94 inches and also for a single day with 9.95 inches on June 8. According to the National Weather Service, precipitation of this magnitude is considered a 1-in-1,000 year event.
Although the current La Niña is coming to an end, Niyogi said that it's likely the weather will continue to be wet all summer. But it's difficult to predict amounts of rain or exactly where it will fall, he said.
“Rainfall is one of the most complex factors in nature,” Niyogi said. “The ground temperature, whether the ground is too wet or too dry, the altitude, the air temperature and humidity all interact to determine where precipitation will fall.”
Many of those factors came together over the southern third of the state during the first two weeks of June, he said. The effect was that a weather pattern of thunderstorms with heavy rain formed over that large area of Indiana and caused flooding. So much rain on already saturated ground, left water with nowhere to go except into homes, businesses and fields that quickly took on the appearance of new swimming pools and lakes.
“It's difficult to say why some areas were hit with widespread heavy precipitation,” he said. “We're still studying why some places receive heavy precipitation and others don't. But we do know that people in Indiana should be prepared for more flooding.”