Scientists at the Hawaiian Volcano Observatory have tightened their forecast for Kīlauea’s 46th lava-fountaining episode, projecting it will begin sometime between May 4 and May 7, 2026. The volcano’s summit has been inflating steadily since the last eruption ended on April 30, and instruments show the shallow magma reservoir is approaching the pressure threshold that has triggered every prior episode in a cycle now stretching back 16 months.
For the roughly 2,000 residents of Volcano Village, located just outside Hawaiʻi Volcanoes National Park, and for the thousands of visitors who pass through the park each week, the forecast means another round of potential air-quality hazards, tephra fallout, and road closures could arrive with little additional warning.
What the instruments show
The observatory’s May 3 volcano message, issued at 9:53 a.m. HST, placed the eruption window at May 4 through May 7. That is a day earlier on each end than the May 5 through May 9 range published just days before, reflecting a faster-than-expected buildup of pressure beneath the summit.
The key gauge is the Uēkahuna tiltmeter, which measures ground deformation caused by magma accumulating in a shallow reservoir. As of the May 3 daily update, the tiltmeter had recorded 13.2 microradians of inflation since episode 45 ended, climbing at a rate of 0.05 to 0.1 microradians per hour. Seismicity remained low: 21 small earthquakes, none exceeding magnitude 2.0. Observers also noted vent glow and open flames at the summit.
That combination of rising tilt, quiet seismicity, and visible vent activity matches the pattern that has preceded each of the 45 prior episodes since the eruption cycle began on December 23, 2024.
Episode 45: the benchmark
The most recent eruption offers the clearest preview of what may come next. Episode 45 began at 1:34 a.m. HST and ended at 10:01 a.m., lasting 8.5 hours. Lava fountains reached a maximum height of 900 feet (270 meters), and the instantaneous peak effusion rate topped 300 cubic meters per second, according to the observatory’s hazard notice. About 5.2 million cubic meters of lava covered roughly half of the Halemaʻumaʻu crater floor.
During that episode, the tiltmeter recorded a deflation of approximately 16.0 microradians as stored magma drained from the reservoir. Scientists use that deflation figure as a rough target: once re-inflation approaches the amount lost, the system is primed for another breach. At 13.2 microradians and climbing, the current inflation is about 82 percent of the way back, which is why the forecast window has tightened.
What remains uncertain
The observatory has not assigned a probability to episode 46 occurring within the forecast window. These windows are living estimates that shift as new tilt and seismic data arrive. A sudden slowdown in inflation could push the eruption later; a burst of faster uplift could pull it earlier. The system has also shown occasional pauses in past cycles when magma supply temporarily waned.
Fountain height is another open variable. While 900 feet is the most recent reference point, prior episodes in this cycle have varied considerably. Some produced shorter, more subdued fountains; others sustained tall jets for hours. No official forecast specifies expected fountain height, effusion rate, or duration for episode 46.
Tephra distribution depends heavily on wind conditions at the moment of eruption. Fine ash and Pele’s hair (thin strands of volcanic glass) can drift several kilometers downwind under strong trade winds, while heavier fragments fall close to the crater. No eruption-specific wind forecast has been published, and general weather models cannot fully account for the turbulence generated by a hot, rising plume.
Health and access considerations
Sulfur dioxide is the primary air-quality concern. During fountaining episodes, SO2 emissions spike dramatically, and the gas reacts with sunlight and moisture to form volcanic smog, or vog, that can drift tens of miles downwind. The Hawaiʻi Department of Health advises people with respiratory conditions such as asthma to limit outdoor exposure when SO2 levels rise, and recommends checking the AirNow network for real-time readings near the summit and in downwind communities like Pāhala and Ocean View.
Hawaiʻi Volcanoes National Park enforces access restrictions during eruptive episodes, though the specific closures for episode 46 will depend on real-time conditions once fountaining begins. In past episodes, areas immediately surrounding Halemaʻumaʻu and portions of Crater Rim Drive have been shut down due to high SO2, ballistic hazards, and the risk of ground cracking. Visitors planning trips to the park in early May should monitor the National Park Service’s current conditions page and be prepared for last-minute road closures, trail shutdowns, and shifting viewing areas.
Why the pattern matters
Forty-five episodes over roughly 16 months have given scientists an unusually rich dataset. Each cycle of deflation during an eruption followed by re-inflation between episodes has repeated with enough regularity that forecasts can now be issued days in advance. That is a notable capability: during Kīlauea’s 2018 lower East Rift Zone eruption, which destroyed more than 700 homes, the timing of individual fissure openings was far harder to predict because the eruption followed a different structural pathway.
The current cycle, by contrast, has kept lava confined to the summit crater, well away from communities on Kīlauea’s flanks. Nothing in the monitoring data as of early May 2026 suggests magma is migrating toward the East Rift Zone or Southwest Rift Zone. The main hazards remain gas, tephra near the summit, and localized disruptions inside the national park.
Still, the observatory’s own language treats each forecast window as an estimate, not a certainty. The shift from May 5 through May 9 to May 4 through May 7 within a matter of days shows how quickly the picture can change. For anyone living near or visiting Kīlauea’s summit, the practical guidance is straightforward: the next several days are primed for renewed activity, conditions can deteriorate within minutes once fountaining starts, and the safest approach is to follow HVO updates in real time rather than plan around a fixed schedule.
More from Morning Overview
*This article was researched with the help of AI, with human editors creating the final content.
