An air quality advisory remains in effect for Prince George after it was first issued Wednesday morning.
Transit in Prince George is also free Thursday, which comes into affect at midnight after air problems are noted.
As part of the city's Free Fare for Clean Air program, free transit will remain until midnight on the day the advisory is lifted.
"Persons in or near this area should be on the lookout for adverse weather conditions and take necessary safety precautions," Environment Canada's weatehr alert said.
High concentrations of coarse particulate matter are expected to persist until there is precipitation, conditions change or the streets are cleared of traction material, the Ministry of Environment said.
Levels tend to be highest around busy roads and industrial operations.
Persons with chronic underlying medical conditions should postpone strenuous exercise near busy streets until the advisory is lifted.
Exposure is particularly a concern for infants, the elderly and those who have diabetes, and lung or heart disease.
All open burning, including backyard burning and land clearing burning, is prohibited during the advisory.
More details on the alert are available at weather.gc.ca/warnings/index_e.html.
