Intense, hot air from the ongoing Kilauea eruption — combined with a drop in trade-winds — triggered 9.22 inches of rain containing sulfur dioxide to drench an isolated portion of the Lower East Rift Zone in the 24 hours that ended this morning at 8 a.m.

“The heat coming out of the lava is making the air mass really unstable,” said National Weather Service meteorologist John Bravender. “We’re not seeing it all the time, but it’s cropping up part of the time.”

The forecast of a return to more conventional tradewind patterns mean heavy rains over the Lower East Rift Zone are likely to dissipate as early as tonight, Bravender said.

In the meantime, he said, as “the lava heats up and rises” it then cools higher in the atmosphere, turns into condensation, then falls as heavy rain that’s “just localized to the specific area where it’s most unstable,” Bravender said.

Tina Neal, scientist in charge of the U.S. Geological Survey’s Hawaiian Volcano Observatory, said ongoing emissions of sulfur dioxide from the eight-mile river of lava likely are falling as “acidic rain” downwind of fissure 8.

No measurements have been taken to determine the level of sulfur dioxide in the rainfall, Neal said.

But, she said, “that rain is acidic. … That likely is occurring.”

Also this morning, the ongoing collapse of Halemaumau Crater from the Kilauea eruption triggered another “explosive event” equal to a 5.3-magnitude earthquake, according to HVO.

As in past “explosive events,” the number of temblors suddenly dropped from 25 to 40 an hour to fewer than 10 an hour following the 9:21 a.m. shaking, which occurred during an operations meeting at Hawaii Volcanoes National Park.

Scientists at HVO expect the number of earthquake-like events to increase over the next 24 hours until the next “explosive event” that’s expected sometime Tuesday as the rim and walls of Halemaumau continue to collapse.

The Pacific Tsunami Warning Center said there was no tsunami threat.

But all of the shaking on Friday opened up “a fairly large sinkhole” on Highway 11 leading into Hawaii Volcanoes National Park, which has now been shuttered for 60 days, said park spokeswoman Jessica Ferracane.

Highway 11 had to be closed down to one lane as state Department of Transportation repair crews repaired the damage by this morning, which included the installation of a steel plate, Ferracane said.

Highway 11 now has a “noticeable big bump and dip” over the old sinkhole and cracks continue to appear in roads throughout the park, Ferracane said.