(AP) — Operators of California’s electricity grid acknowledged Wednesday that a miscommunication led to a small number of power shutoffs during a period of great strain, even as the state faced another day of extreme heat that could prompt much larger rolling blackouts.

The miscommunication occurred Tuesday afternoon between a Northern California utility and the California Independent System Operator as the grid was perilously close to running out of energy, said Elliot Mainzer, president and CEO of the CAISO.

Mainzer told a briefing he did not know specifically how the miscommunication occurred but he stressed the grid operator did not order rotating blackouts.

The CAISO was in the midst of a stage 3 alert and had ordered utilities to prepare to institute load shedding but did not proceed to the final order to do so.

Mainzer said he did not know how many customers were affected when the errant power shutoffs occurred.

Amid the brutal Western heat wave, peak electricity demand Tuesday hit 52,061 megawatts, far above the previous high of 50,270 megawatts set on July 24, 2006.

Mainzer said at approximately 5:45 p.m. Gov. Gavin Newsom triggered a wireless emergency alert system that sent messages to people’s cellphones urging them to turn off or reduce non-essential power.

“Within moments we saw a significant amount of load reduction,” Mainzer said, adding that it took the state back from “the edge.”

The grid will need the same kind of response from consumers Wednesday, only earlier, he said.

Western states are struggling through one of the hottest and longest September heat waves on record. Temperatures began soaring last week and the National Weather Service warned that dangerous heat could continue through Friday, despite some slight moderation.

California’s state capital of Sacramento hit an all-time high Tuesday of 116 degrees (46.7 C), breaking a 97-year-old record.

Sacramento County officials used the air-conditioned lobbies of some of their public buildings as cooling centers for people with nowhere else to go and offering free transportation for people who could not get there. Officials even handed out motel vouchers to some homeless people through a program they normally reserve for the winter, according to county spokeswoman Janna Haynes.

“While a lot of people can stay home, a lot of people do not have a home to stay in,” Haynes said.

In state office buildings, thermostats were being set at 85 degrees (29 C) at 5 p.m. to conserve electricity.

Six places in the San Francisco Bay Area and central coast set all-time record maximum temperatures, including Santa Rosa with 115 degrees F (46 C).

In neighboring Nevada, Reno’s 106 F (41 C) on Tuesday was its hottest day ever recorded in September and smashed the previous record for the date, 96 F (35.5 C) in 1944. It came within 2 degrees of the all-time high for any day or month of 108 F (42 C), set in July 2002 and equaled in July 2007, according to the National Weather Service.

In Utah’s Salt Lake City — a city at more than 4,000 feet (1,219 meters) elevation — temperatures were about 20 degrees higher than normal, hitting 105 F (40.5 C) on Tuesday, the hottest September day recorded going back to 1874.

Scientists say climate change has made the West warmer and drier over the last three decades and will continue to make weather more extreme and wildfires more frequent and destructive. In the last five years, California has experienced the largest and most destructive fires in state history.