A wildfire burning near Marion expanded its footprint by just 17 acres overnight Wednesday, even with critical fire weather threatening much of the region.

The Lemonade Fire was estimated at 636 acres Thursday. It is burning north of U.S. 2 near Ashely Lake and Little Bitterroot Lake. More than 175 firefighters are on the scene.

Hot, dry and windy conditions on Wednesday ramped up fire activity, with short, wind-driven runs on the north flank.

“Heavy equipment operators continued to make progress despite the winds; however, aircraft were grounded for much of the day, and there was limited crew engagement on the southwestern side due to hazard trees,” fire managers reported Thursday.

Two structures are threatened by the fire, with one property under pre-evacuation notice.

Aerial resources were expected to hit the fire Thursday with reduced winds in the forecast. Total cost to fight the fire was estimated at $3.3 million.

Meanwhile, the lightning-caused Margaret Fire burning on the Swan Range about 13 miles east of Bigfork was estimated at 472 acres Thursday. The fire is on a ridge north of Margaret Lake in steep and rocky terrain.

Eight firefighters are assigned to the fire.

In Sanders County, the Bull Gin Complex grew about 350 acres overnight Wednesday. The group of three fires have burned a total of 1,418 acres north of Heron and Noxon on the Kootenai Forest.

No structures are threatened. About 55 firefighters were assigned to the complex. Total cost to fight the fires was estimated at $1.7 million.

A big change in weather is on tap for the weekend as a Canadian cold front moves over the Northern Rockies.

Widespread freezing temperatures are expected for the higher valleys along the divide and east of U.S. 93 in western Montana, the National Weather Service in Missoula reported Thursday.

For valley locations along and west of U.S. 93, lows Saturday morning are expected to be in the mid to upper 30s, with a good chance for widespread frost.

Light rain in the valleys and snowfall on the high peaks in Glacier National Park is possible early Friday morning.