SACRAMENTO (CBS13) – As extreme heat is expected to blanket California through the weekend, the state’s power grid operator issued a new warning late Saturday morning due to continued strain on the power grid.

A Southern Oregon wildfire is threatening transmission lines used to import energy to California, according to the system conditions bulletin issued by the California Independent System Operator (Cal ISO).

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That threat, along with the heat, is putting new stress on the grid. Saturday’s warning allows the Cal ISO to activate emergency demand response programs including rolling blackouts, if needed.

This comes after the Cal ISO issued a Flex Alert for Friday calling on residents to conserve energy to release stress on the grid. Cal ISO said the Flex Alert will remain in place from 4 p.m. to 9 p.m.

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Early Friday afternoon, Cal ISO also issued a grid warning due to wildfires risks stemming from the anticipation of using electricity reserves.

During the Flex Alert, residents are advised to set thermostats to 78 degrees or higher, avoid using major appliances and turn off all unnecessary lights and items that use power.

Triple-digit weather arrived in the Sacramento Valley on Thursday and temperatures are expected to rise well into the 100s Saturday and Sunday.

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Multiple Flex Alerts have already been issued this year as summer-like weather arrived early, as did the start of California’s wildfire season. The most recent alert was issued at the end of June, but Californians’ power conservation efforts helped avoid what would have been the first rolling blackouts of the year.