The ground beneath Kilauea’s summit is swelling again. After 46 explosive lava fountain episodes since December 2024, the U.S. Geological Survey’s Hawaiian Volcano Observatory is forecasting that episode 47 will erupt between Tuesday, May 12, and Friday, May 15, 2026. The volcano is currently in a pause between bursts, but tiltmeter readings show pressure climbing steadily in the shallow magma reservoir beneath Halemaumau crater, following the same pattern that has preceded every fountaining event in this eruption series.
The two most recent episodes offered a stark reminder of how variable these eruptions can be. Episode 45, which fired on April 23, 2026, sent lava fountains to a maximum height of 870 feet (265 meters), taller than a 70-story building and just 30 feet short of the 900-foot mark. Episode 46, which ended on May 5, topped out at 650 feet (200 meters). Both were spectacular. Neither was predictable in scale until they were already underway.
What the observatory has confirmed
The episode 47 forecast window is based on the observatory’s tilt-based model, which tracks the inflation-deflation cycle at Kilauea’s summit. As magma refills the shallow reservoir after each episode, the ground surface tilts measurably outward. When that tilt crosses a threshold, the next fountaining event is imminent. The model has successfully anticipated eruption timing through dozens of cycles since the series began on December 23, 2024.
According to the observatory’s status report for episode 46, the north-vent fountain reached its 650-foot peak while the volcanic plume climbed to roughly 20,000 feet (6,000 meters), high enough to affect aviation routes. The observatory documented peak and average effusion rates, estimated total erupted lava volume, and noted tephra falling downwind, including Pele’s hair, the delicate strands of volcanic glass that form when wind stretches molten lava droplets into filaments.
Episode 45’s 870-foot fountains remain the tallest confirmed in the current series. The observatory published time-stamped overflight imagery for that event, and the measurement stands as the benchmark against which future episodes will be compared.
Between episodes, scientists have been tracking gas pistoning at the vent, a rhythmic rise and fall of lava driven by trapped volcanic gas. The observatory’s Volcano Watch column has described how gas pistoning registers in seismic tremor and sulfur dioxide monitoring data, and how it connects to the pressure buildup that precedes each new burst. That phenomenon is part of what gives forecasters enough lead time to issue multi-day eruption windows before an episode begins.
What no one can predict yet
The observatory has not published a predicted fountain height or effusion rate for episode 47. The tilt model is good at forecasting when an episode will happen but not how big it will be. The swing from 870 feet in episode 45 to 650 feet in episode 46 illustrates the point: gas accumulation in the reservoir, vent geometry, and the speed at which the conduit opens all influence peak height, and none of those variables are fully captured by surface tilt alone.
The variation between recent episodes also raises a broader question about whether the eruption series is evolving. Shorter pauses between episodes combined with fluctuating fountain heights could signal shifting gas dynamics in the magma plumbing system. The observatory’s episode-by-episode dataset logs durations, pause lengths, and maximum fountain heights for every event since December 2024, but no published analysis has drawn a firm conclusion about whether future episodes will trend larger or smaller.
All erupted lava so far has remained within Halemaumau crater, and the observatory has not indicated any threat to surrounding infrastructure. But the eruptions carry consequences well beyond the crater rim. During active fountaining, the aviation color code is raised to RED, alerting pilots to ash and volcanic particles at altitude. The 20,000-foot plume heights recorded in recent episodes are high enough to intersect flight paths over the Big Island. Between episodes, the code typically sits at ORANGE, reflecting ongoing unrest.
What this means for visitors and downwind communities
No specific closure tied to the May 12 through 15 forecast window had been announced by the National Park Service as of the start of that window. The park service manages access to Hawaii Volcanoes National Park independently of the observatory’s scientific alerts, and closures or viewing-area adjustments typically come in real time once fountaining begins and tephra starts falling. Visitors planning trips during this period should check the park’s website and social media channels for updates before heading to the summit.
Downwind communities, particularly on the Kona coast, face a recurring concern during active episodes: vog, the hazy mix of sulfur dioxide gas and fine particles that drifts leeward when trade winds push volcanic emissions off the summit. Sulfur dioxide output spikes during fountaining and can aggravate respiratory conditions, especially for children, older adults, and people with asthma. The Hawaii Department of Health monitors air quality during eruptions, and residents in affected areas are advised to track conditions through the department’s vog dashboard.
The observatory’s time-stamped volcano messages remain the most reliable real-time source once an episode begins, logging fountain height changes, effusion rate milestones, and plume observations as they happen. For anyone watching from a distance or planning around the eruption, those updates are the closest thing to a live account from the scientists running the instruments on the ground.
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*This article was researched with the help of AI, with human editors creating the final content.
