VACAVILLE (CBS13) – The fires surrounding the Sacramento Valley have blanketed the area in a thick cloud of haze.

Terrible air quality is expected all around the valley on Wednesday.

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Last night, smoke from the Napa County wildfires filled the Sacramento area.

School has been canceled for the Fairfield-Suisun School District for the rest of the week.

Vacaville Unified schools remain open, but district officials say they’re taking measures to reduce exposure of students and staff to the smoke. However, students will have excused absences if their parents decide to keep them home.

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A Red Flag Warning is in effect for Northern California from Wednesday into Thursday for gusty winds and low humidity, increasing the fire danger.

At least 17 people have died and at least 2,000 homes, businesses and other structures have been destroyed in the several Northern California wildfires.

Officials still don’t know what exactly started the fires. Conditions were ripe for wildfires in wine country after record rains last winter created an abundance of dry vegetation.

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More than 25,000 people have had to flee for safety from the wildfires.