Impacts to Flathead Lake and Southwest Montana Strong, gusty winds will develop throughout the day on Thursday, leading to potentially hazardous boating conditions on area lakes and elevated fire weather concerns. Flathead Lake: Winds from the West and Southwest will be sustained at 5-15 mph, with gusts from 15 to 25 mph. Boaters should prepare for choppy water and hazardous conditions for the opening of Fall Mack Days. Southwest Montana: Winds will increase into the afternoon out of the South and Southwest. Sustained speeds of 10-25 mph are expected, with peak gusts reaching 20-40+ mph. This, along with warm and dry air, will lead to elevated fire weather conditions.