The U.S. Geological Survey's Hawaiian Volcano Observatory (HVO) says it can no longer model a forecast window for Kīlauea's next lava fountaining episode. In the Hawaiian Volcano Observatory's most recent daily update, issued at 8:23 a.m. HST on Wednesday, September 23, the observatory said irregular changes between summit inflation and deflation have made the timing impossible to model.

That marks a break from a pattern that let HVO issue forecast windows of several days for about 50 of the eruption's 54 fountaining episodes. Overnight from September 22 to 23, the north vent resumed short bursts of lava overflow, with episodes beginning at 10:10 p.m. and 11:44 p.m. HST on September 22 and at 2:46 a.m., 6:10 a.m., and 7:04 a.m. HST on September 23. Each lasted about 30 minutes and was fed by small fountains 30 to 50 feet (10 to 15 meters) high. The Volcano Alert Level remains at WATCH and the Aviation Color Code at ORANGE.

Developing Story Note: This report covers new developments at Kīlauea's summit eruption. Information may change as the Hawaiian Volcano Observatory releases additional updates. Latest verified update: HVO Daily Update, 8:23 a.m. HST, September 23, 2026.

For people on the Island of Hawaiʻi, the change matters because the usual advance notice is gone. HVO also says the likeliest next developments are not expected to produce a strong seismic warning sign, so the next shift in activity could arrive with little lead time.

How the Forecasting Pattern Broke

Since the Halemaʻumaʻu eruption began on December 23, 2024, Kīlauea has followed a steady rhythm. Magma refills a shallow chamber beneath the summit, the ground swells, and fountaining usually begins once inflation recovers the amount lost in the previous episode. Tracking that swelling with tiltmeters allowed HVO to anticipate most episodes.

The rhythm changed after episode 54, a roughly nine-hour fountaining event on August 25 that reached about 500 feet (150 meters). HVO said reinflation afterward was very irregular, with repeated deflations and pauses. On September 7, tiltmeters showed the magma chamber had passed the pressure that typically starts a fountaining episode, yet no high fountains followed. Instead, the north vent produced 104 small precursory overflows between September 7 and 12, and nearly 100 small earthquakes were located in the summit region. On the night of September 14, new vents opened on and near the northwest wall of Halemaʻumaʻu.

In a status report on the summit activity issued September 15, HVO wrote: "It is not possible to forecast an exact outcome of this activity." Summit inflation peaked at about 16 microradians on September 16, then dropped about 2.3 microradians as lava from the new vents stopped. Slow inflation resumed September 17 and recovered about 2.1 of those microradians before roughly 0.3 microradians of deflation began early on September 23, after the overflows resumed.

Scenarios Scientists Are Watching

Drawing on Kīlauea's past episodic eruptions at Puʻuʻōʻō, which began in 1983, and Mauna Ulu in 1969, HVO outlined four possibilities in its September 15 report. Lava could erupt more continuously from vents inside Halemaʻumaʻu. The eruption could return to high fountaining from an existing vent. Magma could open new vents elsewhere in the summit caldera. Or it could move into the upper East Rift Zone or Southwest Rift Zone inside the national park.

In its September 23 update, HVO said the three most likely outcomes are continued activity at the existing north, south, and west vent complex, reactivation of the six new vents, or intrusion into another existing weak crack in the summit area. The north vent has produced the last 11 high fountaining episodes, but HVO said it is "not possible to say with certainty"that the current overflows will lead to another one.

Seismicity and ground deformation remain low in both rift zones. The eruption is occurring within a closed area of Hawaiʻi Volcanoes National Park, where lava has remained throughout this eruption.

Vog, Tephra, and a Hurricane Watch

The practical hazards for residents come from gas and volcanic particles. HVO says sulfur dioxide emissions from the summit typically range from 1,000 to 5,000 tonnes per day between episodes. That gas forms vog, a volcanic haze that can cause respiratory and other problems downwind. During episode 54, HVO received a report of trace Pele's hair, fine strands of volcanic glass, falling in the Kaʻū district. People with asthma or other breathing conditions are among those most sensitive to vog.

The volcano is not the only concern this week. As of 5 p.m. HST on September 23, a Hurricane Watch for Hawaii County was in effect as Tropical Storm Nolo, then about 295 miles south of South Point, was forecast to turn north and approach the Big Island on Friday and Saturday. Forecasters expected Nolo to become a hurricane by Thursday night and possibly a major hurricane by the weekend. They forecast 15 to 20 inches of rain across the Big Island, with up to 35 inches in places, and warned of "catastrophic life-threatening flooding and mudslides" in steep terrain. Hawaii County's mayor issued an emergency proclamation for the storm.

HVO also noted that its monitoring network has mostly recovered from recent power- and storm-related outages, although several summit stations remain offline.

Staying Informed on the Island of Hawaiʻi

HVO posts a daily update each morning and shorter observatory messages when activity changes, and its Kīlauea volcano updates page carries the current alert level. Hawaii County Civil Defense handles local emergency alerts, including any storm evacuation instructions.

On vog days, people in sensitive groups can limit time outdoors and check the vog information resources that HVO recommends. HVO advises residents and visitors to minimize exposure to tephra, which can irritate skin, eyes, and airways.

Visitors planning a trip to Hawaiʻi Volcanoes National Park should check park alerts before driving, especially with Nolo approaching. The caldera rim around Halemaʻumaʻu has been closed to the public since late 2007 because of crater wall instability, ground cracking, and rockfalls. HVO advises anyone along the caldera rim to step away if they feel earthquake shaking.

Because lava has stayed inside the park throughout this eruption, the more immediate household decision this week is storm preparation.

Signals That Would Change the Picture

HVO says it will issue a Volcanic Activity Notice if activity changes significantly. According to its scenarios, new vents opening elsewhere in the summit would likely be accompanied by earthquakes, potentially tightly clustered, along with ground deformation consistent with a new shallow crack. Magma moving into a rift zone would likely show up as an extended period of earthquakes migrating from the summit toward that rift, along with summit deflation.

The next HVO daily update is expected the morning of September 24, HST. The Central Pacific Hurricane Center issues complete advisories on Nolo every six hours, with intermediate advisories in between.

Kīlauea is less predictable now than at any point in this 21-month eruption, but its lava remains inside the park. For Big Island households, the clearest action right now is to prepare for Nolo while watching HVO's morning updates for any change at the summit.

What Readers Want to Know

Is Kīlauea erupting right now?

Yes, at a low level. The summit vents are glowing, producing intermittent spatter, and sending out short lava overflows, but no high fountaining episode was underway as of the September 23 morning update.

Why can't USGS forecast the next lava fountain?

Summit inflation and deflation have changed irregularly since episode 54 in late August, which breaks the pattern HVO used to model the timing of past episodes.

Is lava threatening any homes?

Lava has remained within a closed area of Hawaiʻi Volcanoes National Park throughout this eruption, and the rift zones show no unusual activity.

What is the current alert level?

The Volcano Alert Level is WATCH and the Aviation Color Code is ORANGE, meaning heightened unrest with an increased potential for eruption.

Who should worry about vog?

People with asthma or other breathing conditions are among the most sensitive. They should limit outdoor activity when vog is heavy.

How does Tropical Storm Nolo affect the island?

A Hurricane Watch is in effect for Hawaii County, with heavy rain and possible flooding forecast for Friday and Saturday. Residents should follow Hawaii County Civil Defense and National Weather Service guidance.

When is the next update?

HVO publishes a daily update each morning, Hawaii time, and issues additional notices if activity changes significantly.