Kilauea’s 48th lava-fountaining episode ended on June 1 after sending molten rock roughly 650 feet into the air and coating about 40 percent of the crater floor with fresh flows. Now the Hawaiian Volcano Observatory, a division of the U.S. Geological Survey, expects episode 49 to begin between June 13 and 15, which would make it the volcano’s 49th fountaining event since the current summit eruption started on December 23, 2024. The forecast window has already tightened from a broader 10-to-15-day preliminary estimate issued in early June, reflecting how measured summit inflation after each pause helps scientists sharpen their predictions.
Why USGS expects Kilauea’s record 49th lava fountain matters now
Each pause between fountaining episodes at Kilauea follows a recognizable pattern. Magma refills beneath the summit, the ground inflates, and seismic signals shift until pressure forces a new eruption. The Hawaiian Volcano Observatory tracks these changes in near-real time using tiltmeters and seismic monitoring, and the cumulative inflation recorded since episode 48 ended is what drives the current June 13 to 15 forecast. That window is notably narrower than the preliminary 10-to-15-day outlook HVO published just days after the previous episode stopped.
The narrowing itself tells a story. As tilt data accumulate during a pause, HVO’s internal models gain precision because they can be compared against the behavior of earlier episodes in the same eruption. The observatory has described this approach in its Volcano Watch essays, explaining how inflation trends and subtle changes in seismicity between episodes feed directly into forecast timing. If summit inflation continues on its current trajectory, the June 13 to 15 range should hold or tighten further as new readings arrive. A sudden change in inflation rate, however, could push the onset earlier or later, which is why HVO updates its daily bulletins with fresh measurements and explicit caveats about uncertainty.
For anyone living downwind of Kilauea or planning to visit Hawaii Volcanoes National Park, the practical consequence is straightforward: another episode of lava fountaining is likely just days away, and the hazards that accompany it, including volcanic gas emissions and intermittent ashfall, will return with it. While the eruption is currently confined to the summit crater, vog and fine ash can still affect communities depending on wind speed and direction at the time of the episode.
The evidence behind the June 13 to 15 forecast window
The forecast rests on two primary data streams. First, HVO’s routine update for Kilauea states that forecast models indicate episode 49 of lava fountaining is likely to occur between June 13 and 15. The observatory bases this on summit inflation totals measured since episode 48 ended on June 1, combined with the pattern of pauses observed across 48 prior episodes since December 2024. Each pause has ended after a similar amount of inflation has accumulated, giving scientists a benchmark for when pressure in the shallow magma system is likely to trigger renewed fountaining.
Second, the details of episode 48 itself set the baseline for what might come next. According to the official HVO status report, the most recent episode produced a maximum fountain height of roughly 650 feet (200 meters) and sent lava flows across about 40 percent of the crater floor. Those numbers help calibrate expectations, since fountain heights and flow coverage have varied across the eruption’s nearly 18-month history. Higher fountains often coincide with more vigorous gas release and a greater potential for minor ash production, even when lava remains within the summit crater.
The broader eruption timeline maintained by the USGS confirms that the summit activity has been ongoing since late 2024, with 48 distinct fountaining episodes completed so far. That cadence, averaging roughly one episode every 10 to 12 days, gives HVO a rich dataset for its models. The observatory has also noted that seismic velocity analysis plays a role in projecting when conditions will reach the threshold for renewed fountaining, though the specific velocity values and trigger points have not been published in the public notices.
Taken together, these lines of evidence support the mid-June window: the amount of inflation already observed, the historical pause lengths between episodes, and the consistent way that Kilauea’s summit has re-pressurized during this eruption. While no forecast can eliminate uncertainty, the current range reflects a pattern that has repeated dozens of times since December 2024.
What the forecast does not yet resolve
Several questions remain open heading into the forecast window. HVO’s daily updates reference summit inflation totals but do not publish the exact tilt values or daily inflation increments that feed the models. Without those numbers, outside researchers and the public cannot independently verify whether the inflation curve is tracking precisely toward the June 13 to 15 range or starting to diverge. The observatory’s approach depends on continuous measurement, and any deviation from the expected inflation pattern could shift the onset date by a day or more in either direction.
The scale of episode 49 is also uncertain. Episode 48’s 650-foot fountains and 40-percent crater coverage were notable, but earlier episodes in the sequence produced different heights, durations, and flow extents. Some events have been short-lived pulses, while others persisted long enough to build thicker crusts on the crater floor. HVO has not published a forecast for the intensity or length of the next event, only its likely start date, and emphasizes that eruption behavior can change rapidly once fountaining begins.
Another unresolved issue is how closely the next episode will follow the spatial footprint of earlier ones. So far, activity has remained within the summit crater, and there is no indication from HVO’s public reports that magma is migrating toward the rift zones where flank eruptions can occur. However, changes in seismic patterns or deformation outside the summit could alter the risk profile, which is why the observatory continues to monitor the entire volcano rather than focusing solely on the active vent area.
Ashfall advisories from the National Weather Service have accompanied previous episodes, but the geographic zones and specific warning language for episode 49 will depend on wind conditions at the time of onset. Visitors to Hawaii Volcanoes National Park may encounter temporary closures of overlooks, trails, or sections of Crater Rim Drive if gas concentrations or ashfall exceed safety thresholds. Residents downwind could again see hazy skies and light ash deposits on vehicles and outdoor surfaces, particularly during the most vigorous phases of fountaining.
What residents and visitors should watch for next
In the days leading up to the expected onset, the most useful signals for the public will be HVO’s daily written updates and any special notices issued if deformation or seismicity depart from the current trend. A marked increase in shallow earthquakes beneath the summit or a sharp acceleration in inflation could indicate that episode 49 is imminent, even within the broader June 13 to 15 window.
Local emergency managers and park officials typically use these scientific updates to adjust their own messaging. That may include reminding residents to limit outdoor activity during periods of heavy vog, advising people with respiratory conditions to keep medications handy, and encouraging visitors to check park alerts before driving long distances to summit viewpoints. Because the eruption remains confined to the crater, the primary concerns are air quality and visibility rather than lava directly threatening homes or infrastructure.
For now, the expectation of a 49th lava-fountaining episode underscores how dynamic Kilauea’s summit remains more than a year and a half into this eruption. Each new burst of activity adds to the geological record and offers scientists another opportunity to test and refine their models. For people living on and visiting Hawaii Island, it also means that the spectacle-and the hazards-of one of the world’s most closely watched volcanoes are not finished yet.
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*This article was researched with the help of AI, with human editors creating the final content.
