The United States Geological Survey raised its alert level for Kilauea from Advisory to Watch on September 7, along with the aviation color code from Yellow to Orange, after monitoring instruments picked up precursory activity ahead of what would become the 55th episode of lava fountaining at the volcano’s summit since the current eruption began in late 2024. The change did not mean an eruption was underway. It meant the Hawaiian Volcano Observatory judged conditions close enough to the threshold that pilots, residents and Hawaii Volcanoes National Park visitors needed an earlier heads-up than usual.
An Alert Level Change Built Around Precursory Signals
The Hawaiian Volcano Observatory raised Kilauea’s status after detecting low-level eruptive activity that began around 3:45 p.m. Hawaii time on September 7, a stage the observatory has come to recognize as the reliable early signal that a fountaining episode is approaching. That activity started as a sluggish overflow from the north vent within Halemaumau crater, well short of the sustained, high fountains that mark a full episode.
The observatory’s own notice announcing the change forecast that fountaining could begin anywhere from hours to a few days after the precursory activity started, a window that reflected the eruption’s tendency to build gradually rather than begin without warning.
The Difference Between a Watch and an Actual Eruption
Kilauea’s alert levels run from Normal through Advisory, Watch and Warning, with Watch reserved for a volcano showing heightened unrest or minor eruptive activity posing limited risk. It sits below Warning, the level used once a hazardous eruption is either underway or considered imminent with a high degree of confidence. The September 7 change reflected the observatory’s judgment that conditions had moved past routine background activity without yet crossing into a confirmed eruptive episode.
The parallel jump in the aviation color code, from Yellow to Orange, exists specifically to alert pilots that a volcano is exhibiting heightened unrest with an increased potential for eruption, prompting airlines and air traffic controllers to plan around the possibility of ash reaching cruising altitudes on short notice. The observatory tracks both the volcano alert level and the aviation code on its public status feed for volcanoes currently at an elevated alert level, which listed Kilauea at Watch/Orange following the change.
A 55-Episode Eruption With a Consistent Pattern
Kilauea has been erupting episodically from vents within Halemaumau since December 23, 2024, producing a series of numbered fountaining episodes rather than one continuous eruption. Individual episodes have generally lasted under 12 hours of high fountaining, separated by pauses of two weeks or longer while pressure rebuilds in the shallow magma system beneath the crater.
That pattern is what allows the observatory to anticipate each episode days in advance rather than being caught off guard, since the same sequence of gradually rising gas emissions, ground deformation and small-scale precursory activity has preceded most of the prior 54 episodes in the current eruption.
Why the Timeline Kept Shifting
Forecasting the exact start of episode 55 proved harder than usual in the days after the alert level changed. Monitoring data showed the pace of magma recharge beneath the summit behaving irregularly compared with earlier episodes, pushing the expected fountaining window later than the observatory’s initial estimate and underscoring that precursory activity signals an approaching episode without pinning down its precise start to the hour.
That uncertainty is built into how the observatory communicates the forecast, which is framed as a range of days rather than a fixed appointment, precisely because the underlying plumbing feeding each episode does not behave with mechanical regularity. Similar shifts in timing have occurred before in the current eruption sequence, with several past episodes arriving a day or more later than the observatory’s initial estimate once gas emissions and tilt measurements settled into a clearer pattern.
Why Kilauea Carries a Very High Threat Ranking
The United States Geological Survey classifies Kilauea as a Very High Threat volcano under the National Volcanic Early Warning System, a ranking based on both its eruptive history and its proximity to residential areas, roads and Hawaii Volcanoes National Park. The classification is one of only a small number nationwide, reflecting a combination of frequent activity and the number of people and structures within range of its hazards.
The Hawaiian Volcano Observatory’s continuous monitoring network, including seismometers, ground-deformation sensors and gas-measuring equipment, is what allows the agency to catch precursory signals like the September 7 overflow early enough to raise public awareness before fountaining begins rather than after. That network has operated through more than 50 prior episodes of the same eruption, building the comparative baseline the observatory now uses to judge whether a given signal is routine or worth an alert-level change.
What Residents and Park Visitors Were Told to Expect
Hawaii County Civil Defense and Hawaii Volcanoes National Park have generally used prior alert-level changes as a cue to remind residents and visitors that fountaining episodes can produce volcanic fume, or vog, downwind of the crater, along with the possibility of tephra, small fragments of volcanic rock and glass, settling near the vent area. Local coverage of the September 7 change noted the park’s summit overlooks remain the primary public vantage point for viewing episodes from a safe distance once fountaining begins.
None of Kilauea’s episodes in the current eruption sequence have threatened areas outside the closed summit region, and the park has kept trails and roads near Halemaumau closed specifically because of the hazards fountaining produces at close range, rather than any risk extending into surrounding communities.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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