FOLSOM (AP) – California’s power grid operator called for voluntary conservation of electricity Thursday as high heat gripped the state.

The California Independent System Operator issued a Flex Alert for the period from 3 p.m. to 10 p.m. due to an expected increase in electricity demand, primarily from use of air conditioning.

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Late afternoon and early evening is when the grid is most stressed and solar power production falls.

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The heat is being produced by a ridge of high pressure covering the entire West and extending into Alaska, the National Weather Service said.

In mid-August, a heat wave strained the grid to the point that the operator ordered utilities to implement rolling blackouts.

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