A forest fire burning near kilometre 280 of the Dempster Highway is affecting travel.

The 40 hectare fire was one of five new fires sparked in the Yukon on Tuesday.

"It started about two kilometres west of the highway but has since moved and jumped the highway, so it's burning on both sides," says Yukon Wildland Fire Management spokesperson George Maratos.

"The fortunate thing is the winds are quite light."

Pilot vehicles are available, if necessary, to guide traffic through the smoky conditions from kilometre 280 to kilometre 286.

Maratos says lightning caused the fire. He says there were 400 lightning strikes in the Eagle Plains area yesterday.

Elsewhere, the fire danger rating is currently "extreme" in the Carmacks and Haines Junction regions.