Published May 1, 2026
The ground beneath Kilauea’s summit is swelling again, and the U.S. Geological Survey says the volcano’s next explosive lava fountain could erupt within days. In a hazard notification issued April 30, the Hawaiian Volcano Observatory projected that episode 46 of Kilauea’s ongoing fountaining sequence will occur between Tuesday, May 5, and Friday, May 9. If recent episodes are any guide, the burst could send a column of molten rock 700 to 900 feet into the sky above Halemaumau crater and push an ash plume high enough to disrupt flights across the Big Island.
“We use the tilt record to project when the next episode is likely to begin, and that method has performed well over the last several cycles,” said Ken Hon, scientist-in-charge at the USGS Hawaiian Volcano Observatory, in the agency’s Volcano Watch bulletin analyzing episode 44. “But with some of our tiltmeter stations currently experiencing outages, there is additional uncertainty in the forecast window.”
Tilt data points to a five-day eruption window
The forecast hinges on tiltmeters, sensitive instruments bolted to bedrock around the summit that measure how the ground surface deforms as magma pools beneath it. When inflation crosses a threshold, pressure forces magma upward and a fountain episode begins, typically lasting several hours before the system deflates and the cycle resets.
Over the course of 45 episodes, HVO scientists have sharpened this tilt-based forecasting method into a surprisingly reliable tool. A USGS Volcano Watch analysis of episode 44, which produced fountains reaching roughly 800 feet, described how inflation trends allow the observatory to project the timing of each new burst days in advance. The forecast for episode 45 landed within its predicted window, reinforcing confidence in the current May 5 through May 9 projection.
There is a complication, though. The April 30 notice acknowledged that some tiltmeter stations at Kilauea are currently experiencing outages. Because tilt data is the primary input for the forecast model, those gaps introduce real uncertainty. If instruments come back online or backup stations compensate, HVO could narrow or shift the window in the days ahead.
Episode 45 set the bar for what comes next
The most recent eruption, in late April, offers the clearest preview of what episode 46 could deliver. According to the USGS status report for episode 45, the main body of the lava fountain reached at least 700 feet, with thinner wisps of molten material occasionally climbing above 1,000 feet. The volcanic plume rose to roughly 20,000 feet above sea level, prompting the National Weather Service to issue an ashfall advisory for communities downwind of the summit.
Lava output was equally striking. The instantaneous peak effusion rate hit just over 300 cubic meters per second, while the average across the episode settled near 170 cubic meters per second. At those volumes, fast-moving flows can reshape the crater floor and send rivers of lava across previously cooled surfaces in minutes. Episode 44, by comparison, topped out at about 800 feet, suggesting the sequence has maintained or slightly increased its energy from one burst to the next.
Satellite imagery captured by NASA’s Earth Observatory confirmed the scale from orbit, with remote-sensing instruments detecting both the thermal signature of the lava and the height and drift of ash plumes. That orbital perspective is especially valuable when ground instruments are partially offline, because thermal sensors can still register eruptive activity even if local monitoring briefly falters.
What the data cannot tell us yet
The headline figure of 900 feet reflects the upper range observed across episodes 44 and 45, where the main fountain body reached 700 to 800 feet and wisps exceeded 1,000 feet. No USGS document provides a specific height prediction for episode 46. Whether the next burst matches, exceeds, or falls short of those benchmarks depends on how much magma accumulates before the pressure threshold is crossed, a variable that tiltmeters track in near-real time but cannot pin down with precision days in advance.
Scientists also have not said publicly whether the sustained intensity and shortening intervals between episodes signal a shift toward a different eruption style, such as prolonged lava effusion rather than discrete fountaining bursts. The pattern so far has been remarkably consistent: pressure builds, releases in a dramatic fountain, then resets. Whether that cycle holds through episode 46 and beyond is an open question the observatory is watching closely. For now, HVO’s communications emphasize episode-by-episode forecasting rather than long-range predictions about how the eruption might evolve.
Vog, ash, and air quality across the Big Island
Even when lava stays inside Halemaumau crater, the eruption’s reach extends well beyond the summit. Sulfur dioxide emissions during fountain episodes feed vog, the volcanic smog that drifts southwest and can blanket Kona-side communities from Kailua-Kona down to Ocean View. During episode 45, the NWS ashfall advisory highlighted the potential for fine particulate matter to degrade air quality tens of miles from the vent.
“When we get an ashfall advisory, we tell people to bring pets inside, cover water catchment systems, and avoid driving through heavy ash if they can help it,” a Hawaii County Civil Defense spokesperson said during a public briefing following episode 45. “The eruptions are spectacular, but the air-quality effects are the part that actually reaches people’s homes.”
People with asthma or other respiratory conditions should have N95 masks on hand and follow guidance from the Hawaii Department of Health about when to limit outdoor activity. Drivers downwind should watch for reduced visibility if ash begins to fall, and should avoid stopping on narrow roads to watch the eruption, which can block emergency vehicles and create hazards on winding summit approaches.
What Big Island residents and visitors should do before May 5
For anyone living near Kilauea or planning a visit during the forecast window, the most practical step is to plug into official alert channels now, before the next episode starts. The USGS Volcano Notification Service delivers updates by email as conditions change. Hawaii County Civil Defense posts road closures and shelter information. The National Weather Service issues ashfall and air-quality advisories that cover specific zones and timeframes.
Visitors should check Hawaii Volcanoes National Park announcements before driving toward the summit. Access to overlooks and trails near Halemaumau can change rapidly once fountaining begins, and the park has closed sections of Crater Rim Drive during previous episodes to protect public safety. Being turned away at a gate after a long drive is frustrating but predictable; checking the park’s website or social media feeds that morning can save the trip.
How HVO’s episode-by-episode forecasting keeps pace with Kilauea
Above all, it is worth remembering that the May 5 through May 9 window is a probability range, not a countdown clock. The eruption could arrive at the early edge, the late edge, or slightly outside the window if conditions shift. Treating Kilauea as the active, evolving volcanic system it is, rather than a scheduled show, and relying on verified information from HVO and civil defense will keep people safer than any social media livestream can.
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*This article was researched with the help of AI, with human editors creating the final content.
