NEW YORK (Reuters) - State utility regulators will vote Thursday on Southern California Edison's wildfire-mitigation plan, which safety auditors have said does not properly assess the risk of blazes during extreme winds, filings show.

SCE's updated 2025 wildfire-mitigation plan before the California Public Utilities Commission carries added weight in metro Los Angeles, where powerful Santa Ana wind gusts spread catastrophic blazes this month in what is expected to be the most costly natural disaster in U.S. history.

Fire officials have not found SCE, a unit of Edison International, to be responsible for the fires. But the company's infrastructure is being investigated and it faces several lawsuits alleging its equipment sparked the destructive Eaton Fire.

The PUC is expected to vote on whether to ratify an auditor's approval of SCE's latest wildfire mitigation plan, which utilities develop to reduce fire risk.

While the auditor found SCE's overall plan meets and sometimes exceeds the plans of its peers, the company's assessment of wildfire dangers from severely strong winds could be underestimating the risks, it said.

SCE relies on wind-condition data representing the past 20 years that does not consider rare but foreseeable and significant risks, according to an audit by the California Office of Energy Infrastructure Safety.

"SCE's current risk model scenarios do not do enough to predict current and future wind-related fire risks, as it doesn't consider the severe wind events and increasing weather extremes brought on by climate change," the agency said in an email to Reuters. The agency has told the utility its approach could be improved to "better meet fundamental mathematical standards and make proper mitigation prioritization decisions."

SCE DEFENDS CALCULATIONS

SCE spokesperson David Eisenhauer said the utility believes its calculations are appropriate.

"We do incorporate the probability of ignition, informed by the frequency of fire weather and wind information, as well as asset health, vegetation growth rates and other factors," Eisenhauer said.

Threat assessment is important because it guides how utilities spend billions of dollars on the infrastructure and equipment that delivers electricity to homes and businesses. The cost of SCE's wildfire mitigation plan for 2023-2025 is estimated at $5.6 billion.

The utility has told regulators it plans to bolster historical weather scenarios and consider future conditions such as climate change in its upcoming 2026-2028 wildfire mitigation plan, disclosures by SCE show.

Throughout the U.S. power industry, climate scientists and engineers are revising how they calculate the odds of the next natural disaster and how to best prepare the grid to mitigate the damage.

Risk models used by regional grid operators and large utilities have often considered decades of historical data and assign each year's weather an equal chance of occurring in the future. With that approach, the full impact of more recent and frequent wild weather may be underestimated, a 2022 Reuters report found.

As the frequency of catastrophic wildfires escalates, SCE uses estimates of worst-case scenarios to guide its mitigation measures.

SCE and other utilities have come under increasing scrutiny over their response to the California disaster.

SCE is the largest electric utility in Southern California, and has been targeted in multiple lawsuits that accuse the company's infrastructure of sparking the deadly Eaton blaze in the hills above Altadena last week.