KAMLOOPS, B.C. -- Access to the backcountry has been banned in a large swath of British Columbia's Interior as wildfire crews gear up for a challenging weekend.

Kevin Skrepnek with the BC Wildfire Service said winds are expected to pick up Saturday with a change in the weather and that risks fuelling fires already burning throughout the Cariboo fire centre.

The ban started Friday and covers 103,000 square kilometres of Crown lands within the Cariboo region in south central B.C.

Skrepnek said the ban is intended to maintain safety and prevent any human-caused fires that could divert their resources at a time of extreme fire danger.

The restriction means people cannot stay in or enter the area without the prior written authorization. It will remain in place until Sept. 5 but can be lifted earlier if conditions improve.

Thunder showers are in the forecast for the weekend, but Skrepnek said any rain in the Interior is likely to be "patchy" and not enough to douse fires.

"This rain appears to be a fairly temporary fixture. It might buy as a few days of relative reprieve on some fires, but we don't know yet how much rain is going to fall, where it's going to fall and how long it's going to linger for," he said.

Whether any more rain moves in after Monday is "anyone's guess," Skrepnek said.

Commercial operations, people travelling on an official capacity or to their primary residence, travellers using highways and those helping in the firefighting effort are exempt from the backcountry restriction.

Exemptions are also in place for the historic town and park of Barkerville, adventure tourism operations and guide outfitters that depend on access to the landscape for business, Skrepnek said.

The Cariboo region spans from Loon Lake near Clinton in the south to the Cottonwood River near Quesnel in the north, and from Tweedsmuir Provincial Park in the west to Wells Gray Provincial Park in the east is popular among hikers and campers.

There were 148 active fires across the province Friday.

Two more evacuation orders were implemented Friday for sparsely populated areas of the Cariboo near Quesnel Lake and Maeford Lake. People in both communities were told to head to a reception centre in Prince George.

This fire season has burned an estimate 6,460 square kilometres, and is being called unprecedented by officials. That figure is the second-highest area recorded burned in the province since 1958.

"To put that into perspective, that is more than double the size of Greater Vancouver, including the Fraser Valley, North Shore Mountains towards Aldergrove and Maple Ridge as well," Skrepnek said, adding the total burned area is still likely to grow.

The smoke billowing from the fires has resulted in air quality advisories for most of the province.

A low pressure system moving in this weekend was expected to clear the air for coastal B.C. Skrepnek said it's affect on the Interior would depend on winds and the number of fires that continue burning.

Health officials are warning anyone with chronic respiratory conditions to have their medications on hand and have a plan of how to get medical assistance in an emergency.