The Binta Lake fire has grown to 310 square kilometres. (CBC)Ash from wildfires in B.C.'s Cariboo region is falling like snow in Williams Lake, where the Environment Ministry has rated the air quality the poorest in the province.

Guests at a hotel in the city are complaining about conditions that are causing some to cough and wheeze, said Katrina Buckland, who works at the front desk.

"When you go outside after about nine o'clock when it gets dark here, all the ash in the air, you can actually see it falling, and we've been making a joke that it's actually snowing in August around here," she said.

Intense, choking smoke from wildfires in the Cariboo is also affecting air quality in Kamloops, B.C., where stores began closing their doors and residents were asked to stay inside.

Smoke drifting as far east as Alberta has prompted the province's chief medial officer of health to warn residents with breathing problems to say indoors.

B.C.'s Environment Ministry advised children and the elderly to avoid strenuous outdoor activities.

Smoke concentrations in the Thompson Valley will vary widely, depending on winds, temperatures and forest fire activity, the ministry said.

Flights cancelled

Six Air Canada Jazz flights in and out of the Kamloops, B.C., airport were cancelled late Thursday because of poor visibility.

The airport is asking travellers and those expecting flights to check its website to determine if flights are delayed.

Forest service planes began checking huge areas of B.C.'s charred woodlands early Thursday morning, trying to determine if erratic overnight winds caused any wildfire flare-ups.

Fire information officer Gwen Eamer said the northwestern corner of the province took the brunt of a weather system, packing winds of up to 60 kilometres an hour.

Smoke billows thousands of metres into the air from the Binta Lake fire. (CBC)She said blazes in the Bulkley-Nechako area, on the inner central coast, grew significantly while 52 active fires in the Cariboo region of the central Interior were not as hard hit.

More than 2,200 people have been forced out of their homes across the province during the last three weeks, said Shelly Burich, a spokeswoman for the Cariboo Regional District.

Burich said some people have been able to return, but others have had to leave their properties more than once.

Some evacuees return

Improved conditions on Thursday meant several evacuation alerts and orders were lifted within the regional district, Burich said.

An evacuation alert for residents of 439 homes from the central Chilcotin has been lifted, as was an evacuation order for people from 306 properties in the Anahim Lake area and Heckman Pass.

Most fires in the province grew by only five or 10 per cent overnight, significantly less than originally anticipated, Forests Minister Pat Bell said.

However, Bell said a fire at Binta Lake, about 500 kilometres north of Vancouver, has grown threefold to about 310 square kilometres.

"We're watching this one very closely," he said.

Chris Duffy, director of operations for Emergency Management B.C., formerly known as the Provincial Emergency Program, said people from 728 properties are currently out of their homes across the province and that a further 1,138 homes are on evacuation alert.

About 270 fires were still active across the province late Thursday.

More than 1,980 square kilometers of forest have burned in B.C. so far this year, according to ministry figures.