The ground beneath Kīlauea’s summit is rising again, and the clock is ticking toward another spectacular, hazardous eruption. The U.S. Geological Survey’s Hawaiian Volcano Observatory now expects the 48th lava-fountaining episode of the current eruption cycle to begin sometime between Sunday, May 25, and Tuesday, May 27, 2026, based on the pace at which magma is re-pressurizing the volcano’s shallow plumbing system. The agency is holding Kīlauea at a Volcano Alert Level of Watch and an Aviation Color Code of Orange, one step below the highest tier.
The forecast follows a pattern that Big Island residents have come to know well since this eruption cycle began in late 2024. Magma pools beneath the summit, the ground inflates like a slow-motion balloon, and when pressure exceeds what the rock can contain, lava fountains erupt from vents inside Halemaʻumaʻu crater. Episode 47, the most recent burst, began and ended on May 15. It lasted only nine hours but sent fountains roughly 650 feet (about 200 meters) into the air and spread an estimated 5.2 million cubic meters of lava across the crater floor, according to the observatory’s status report.
Why scientists expect another episode within days
The primary tool driving the forecast is a sensitive tiltmeter at the Uēkahuna station (station code UWD), perched on the northwest rim of the caldera. During episode 47, the instrument recorded 15.6 microradians of deflation as magma drained from the reservoir and erupted at the surface. Think of it as a pressure gauge: the eruption released a measurable amount of stored energy, and now the gauge is climbing back up.
By May 18, just three days after episode 47 ended, the tiltmeter had already recorded 8.4 microradians of re-inflation, meaning the summit had recovered more than half the pressure it lost, according to an HVO notice. The observatory projects when the tilt will reach a threshold derived from the prior episode’s deflation, then sets a public forecast window around that date. If inflation speeds up, the window shifts earlier; if it slows, the window stretches.
That sensitivity explains why the forecast has already shifted once. An earlier bulletin dated May 18 placed the window from May 22 through May 25. The most recent daily update pushed it to May 25 through May 27, reflecting a slight deceleration in the inflation rate. HVO has published a detailed explainer on its forecasting method, noting that instrument drift and network outages can also affect calculations.
What episode 48 could look like
No two episodes are identical, and HVO has cautioned that the scale of the next event depends on how much magma accumulates before the system ruptures. Episode 47 was short but violent, with towering fountains and heavy tephra fall. Earlier episodes in the cycle have varied from a few hours to more than a day, with fountain heights ranging from under 100 feet to well over 600.
Once fountaining begins, the Washington Volcanic Ash Advisory Center will issue aviation advisories based on satellite imagery from GOES-18, direct HVO observations, and data from the Honolulu Meteorological Watch Office. During episode 47, ash and tephra prompted alerts that can reroute flights across the central Pacific.
Sulfur dioxide emissions are another major concern. During active fountaining, SO₂ flux spikes sharply, and trade winds can carry volcanic smog, known locally as vog, across the island’s leeward communities. Vog aggravates asthma, irritates eyes and airways, and can damage crops. HVO publishes SO₂ ranges in its daily updates, but real-time flux measurements between episodes are not released publicly, limiting independent verification of how quickly gas output is building.
Closures, road impacts, and what to prepare for
Hawaiʻi Volcanoes National Park has a well-practiced closure protocol. During episode 43 in March 2026, the National Park Service reportedly shut down the summit area and a segment of Highway 11, the main route along the island’s south side. Access reopened after crews cleared debris and air quality returned to safe levels. Visitors should expect similar restrictions during episode 48, potentially with little advance notice if activity ramps up quickly or wind shifts push ash over viewing areas.
Hawaiʻi County Civil Defense has issued standing guidance for eruption periods: protect rainwater-catchment systems by disconnecting or covering intake lines before ashfall arrives, limit outdoor exposure during poor air quality, and drive cautiously when visibility drops. Residents with respiratory conditions should have N95 masks and eye protection on hand.
For visitors hoping to witness the eruption, flexibility is essential. Park closures can last hours or days. Travelers should monitor the official park website and HVO’s update page, check road conditions before driving at night, and follow all ranger instructions. Drone use is prohibited inside the park, and entering closed areas puts both individuals and rescue crews at risk.
What scientists still cannot predict
The forecast window is a probabilistic estimate, not a countdown to a specific hour. Tilt data alone cannot fully predict when magma will break through to the surface, because that depends on subsurface rock strength and conduit geometry that instruments cannot directly image. Seismic tremor, gas output, and visual observations will all feed into real-time assessments once activity begins, but those signals can shift rapidly.
Several data gaps also limit outside analysis. No publicly available time-series of tilt readings between the May 18 snapshot and the present has been released, so the exact inflation trajectory is known only to HVO staff. And no Washington VAAC advisory for episode 48 exists yet, because the eruption has not started.
None of that diminishes the forecast’s value. HVO’s willingness to update its windows as new data arrive reflects an evidence-driven approach, and the observatory’s track record across 47 prior episodes gives the model a substantial performance history. The two slightly different windows published days apart are not a sign of confusion; they are the forecast working as designed, adjusting to what the volcano is actually doing.
Where to get reliable updates as the window opens
As Sunday approaches, the most trustworthy information will come from HVO’s volcano updates page, the National Park Service’s alerts for Hawaiʻi Volcanoes National Park, and Hawaiʻi County Civil Defense bulletins. Together, those sources paint a clear picture: Kīlauea’s summit is re-pressurizing fast, another fountaining episode is likely within days, and communities, travelers, and airlines should be ready for short-term disruptions while the volcano decides its own schedule.
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*This article was researched with the help of AI, with human editors creating the final content.
