Photo: Twitter - BC Wildfire Service

Weather continues to be the main challenge for crews fighting a series of wildfires in northeastern B.C., including a large blaze that has crossed the provincial boundary into Alberta.

The Siphon Creek fire entered Alberta late Thursday and is now burning one or two kilometres into the province, said BC Wildfire Service spokesman Kevin Skrepnek.

He said the fire is estimated to be about 170-square kilometres and remains uncontained after being sparked April 18, about 60 kilometres northeast of Fort St. John.

Forests Minister Steve Thomson said 77 B.C. firefighters, nine helicopters and heavy equipment are fighting flames on both sides of the boundary in an effort to help their Alberta counterparts who are busy dealing with a devastating fire in Fort McMurray.

"The situation in Fort McMurray and in the B.C. Peace continues to worsen," Thomson said.

Christopher Duffy with Emergency Management B.C. said residents at 11 B.C. addresses have been ordered to evacuate and 50 more are under evacuation alert. Residents in Clear Hill County, Alta., are also under evacuation alert.

People living near the Beatton Airport Road fire, burning 50 kilometres northwest of Fort St. John, have also been chased from their homes by the flames.

The fire merged with another blaze Thursday and now covers an estimated 120-square kilometres.

Durffy said about 500 people have either been forced to evacuate because of the fire or have been notified that they may need to leave at a moment's notice.

The fire is continuing to grow aggressively, and hot, dry weather is not helping, Skrepnek said.

Rain is expected Sunday, he said, but it will likely bring gusting winds that may fan flames.

"When a lot of these fires first started in the Peace a few weeks ago, we were seeing record-breaking temperatures, unusually and unseasonably dry conditions and then it turned into a perfect storm when we had a pretty significant wind event come through," Skrepnek said.

The conditions have created fast-moving, stubborn fires that are tough to contain, he added.

"I think, looking across the border to Alberta, they're seeing a similar weather pattern there, and certainly the activity in Fort McMurray on Tuesday seems to be largely wind-driven as well."

Skrepnek said there are currently 81 fires burning across the province, and 213 have been sparked since April 1, burning more than 300-square kilometres.

Thomson said many of the fires were human caused.

"This is a collective responsibility that everyone has to act responsibly. And we're going to continue to communicate that. It remains a frustration."