LAKE COUNTY, Calif. – Lake and neighboring counties are under a heat advisory through Sunday night due to a forecast that calls for temperatures expected to top the century mark.

The National Weather Service issued the heat advisory, in effect until 8 p.m. Sunday.

The agency said a heat advisory means that a prolonged period of hot temperatures is expected and will create a situation in which heat illnesses are possible.

Forecasters are predicting daytime highs in the upper 90s and lower 100s around the region.

The specific Lake County forecast calls for daytime temperatures as high as 104 degrees on Saturday and 105 degrees on Sunday, with nighttime temperatures in the 60s.

Much of Mendocino County is under the same heat advisory, according to the National Weather Service.

The high temperatures are a concern for firefighters, who are battling the Mendocino Complex of fires – consisting of the Ranch and River fires – that began Friday.

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