Related: Heat, Wind Could Mean Trouble For Oregon Wildfires

The National Weather Service says last month was the hottest August on record for Portland and Salem.

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Even the coast experienced warmer-than-normal temperatures. Astoria experienced its third hottest August on record.

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And summer isn't over yet. Hot temperatures are expected to spill into September as well; meteorologists say it's hard to predict when the heat will let up.

"It's just a big warm air mass over the area with not a lot of change in the weather pattern," said Treena Jensen, a senior meteorologist with the National Weather Service.

Temperatures in the Willamette Valley will rise into the 90s Friday and will go up from there, Jensen said. Much of the state will experience these hot temperatures too. Some places will reach 100 degrees.

Jensen says it's not unusual to have heat spells in the beginning of September — and sometimes even October. Temperatures start to cool off by mid-September.

It's been a year of record-breaking heat and dryness, a dangerous combination for firefighters battling thousands of acres of fires.

"We're expecting the fires south of us to increase in their activity over the weekend," Jensen said. "Some of that smoke will blow into our area. So there also be some air quality concerns."