* WHAT. North to east winds 20 to 35 mph with gusts up to 55 mph possible. * WHERE. Flathead/Mission Valleys. * WHEN. From Monday evening through Tuesday morning. * IMPACTS. Damaging winds could blow down trees and power lines. Widespread power outages are possible. Travel could be difficult, especially for high profile vehicles. It could be dangerous for boaters to be on Flathead Lake and other lakes Monday evening. If you are camping or recreating outdoors during this time, avoid setting up tents or campers near trees. Winds over 40 mph could easily bring down weakened trees or large limbs, especially in forested areas and western foothills prone to downslope winds. Be prepared for rapidly changing conditions. * ADDITIONAL DETAILS. This is a rare storm to occur in the month of July. A strong cold front from Canada will push south and west across the region Monday evening. The strongest winds will occur in the higher elevations, and along Flathead Lake. Thunderstorms are possible Monday night into Tuesday morning and the main threats could be lightning, gusty winds, hail and heavy downpours.