People with chronic medical conditions should avoid strenuous exercise until the advisory is lifted.
The Ministry of Environment is urging anyone experiencing eye or throat irritation, chest discomfort, coughing, wheezing or shortness of breath to seek medical help.
Prince George's bylaws prohibit open burning, including backyard burning and land-clearing burning.
During advisories, recreational fires and street sweeping activities are prohibited.
Businesses and residents are asked to reduce emissions as much as possible during the advisory.
There are 51 fires in the Prince George area, and a total of 200 fires provincewide.
Lightning sparked most of the 91 new blazes that started this weekend.
The fires do not appear to be affecting populated areas, though an evacuation order has been issued in the Chelaslie River area, west of Prince George.
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