Kilauea’s summit is swelling again. Just two days after lava fountains shut off at the end of episode 46, instruments on the volcano’s western caldera rim show magma pressure rebuilding at a pace that has preceded every major fountaining event in this five-month-old eruption. The Hawaiian Volcano Observatory’s daily update on May 8, 2026, placed a preliminary forecast for episode 47 between May 12 and May 17, giving Big Island residents, downwind communities, and national park visitors roughly a week’s notice before the next round of fire.
What the instruments show right now
The forecast hinges on a single, continuously updated data stream: the radial tiltmeter at Uekahuna (station code UWD), perched on Kilauea’s western caldera rim with a direct read on deformation caused by magma shifting beneath the summit. During episode 46, which ran from 8:17 a.m. on May 5 to 5:22 p.m. on May 6, UWD recorded approximately 14.0 microradians of deflation as magma drained from the shallow reservoir into the erupting vent inside Halemaumau crater.
Since the fountains stopped, the same instrument has logged roughly 6.9 microradians of inflation, meaning the summit has already recovered about half of the ground tilt it lost during the eruption. HVO uses that recovery ratio as a key input for its episode forecasts. In recent months, new fountaining has tended to begin within days of the tilt returning to its pre-episode level. At the current pace, that threshold falls squarely inside the May 12 to May 17 window.
The eruption sequence stretches back to December 23, 2024, when lava returned to Halemaumau crater after months of quiet. The USGS episode table now lists 46 completed fountaining events, some producing lava jets topping 200 feet and sending volcanic gas plumes thousands of feet into the trade-wind layer. Episode 46 itself lasted roughly 33 hours, a duration broadly in line with the range seen across the sequence.
Alert levels have tracked each cycle. HVO raised Kilauea to WATCH/ORANGE on May 4 as precursory signals intensified ahead of episode 46, then dropped it back to ADVISORY/YELLOW once the fountains stopped. That is where the volcano stands during the current pause. The Smithsonian Institution’s Global Volcanism Program archived the same status in a May 4 report, drawing its information from HVO’s data stream.
Why the window could shift
HVO labeled the May 12 to May 17 forecast “preliminary” for good reason. While the eruption has followed a broadly rhythmic pattern, the spacing between episodes has varied by days. Some pauses have lasted fewer than 48 hours; others have stretched close to a week. Individual episodes have also differed in fountain height, duration, and lava volume, a reminder that the volcano’s plumbing does not run on a fixed clock.
Several variables remain unresolved. The observatory has not published projected plume heights or lava output estimates for episode 47, and no sulfur dioxide emission rates specific to the post-episode 46 pause have appeared in public data yet. A USGS dataset covering 2023 through 2025 shows that peak fountaining events can push SO₂ output into the range of thousands to tens of thousands of tonnes per day, but whether episode 47 will match that depends on how completely the shallow reservoir refills and how gas-rich the incoming magma is.
HVO scientists have also described a transitional behavior called “gas pistoning” that often precedes full fountaining. During gas pistoning, trapped gas drives cyclic rises and falls of lava in the vent, producing distinctive tremor bursts and fluctuations in SO₂ output. The observatory has linked this pattern to pre-eruption conditions in past episodes, but the exact moment it escalates into sustained fountaining is not precisely predictable. Instruments are watching for those tremor signatures now.
Crater-floor elevation data, another metric HVO tracks, has not been updated beyond the past-week plot window, leaving a gap in the public evidence base. Small elevation changes can reflect significant shifts in magma volume, so the next topographic update could either reinforce or tighten the current forecast.
How the UWD tilt curve will signal the next fountain
For communities on the Big Island’s Kona side and in Ka’u, the most immediate concern during a fountaining episode is vog, the haze of sulfur dioxide and fine particulate matter that drifts downwind when trade winds carry volcanic emissions off the summit. Prolonged exposure aggravates asthma and other respiratory conditions, and past episodes in this sequence have pushed air-quality readings into unhealthy ranges for sensitive groups in parts of West Hawaii. The Hawaii Department of Health maintains real-time air-quality monitors, and residents with respiratory conditions should track those readings as the forecast window approaches.
Hawaii Volcanoes National Park remains open during inter-episode pauses, though access to certain overlooks near Halemaumau can be restricted when fountaining resumes or gas concentrations spike. The park’s website and social media channels post closures in near-real time. For visitors hoping to witness a fountain, the USGS publishes live tilt plots, seismicity charts, and webcam feeds that offer the clearest public window into the volcano’s pressure buildup.
The number to watch is the UWD inflation curve. When it climbs back toward the 14-microradian mark that preceded episode 46, the next fountain is likely close. If inflation stalls or accelerates unexpectedly, HVO has a track record of revising its preliminary windows, sometimes narrowing them to a day or two once deformation and seismicity cross key thresholds. Until then, the May 12 to May 17 outlook stands as the observatory’s best current estimate for when Kilauea will light up again.
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*This article was researched with the help of AI, with human editors creating the final content.
