SXUS45 KMSO 312330 RECGPI Recreation Forecast for Flathead Lake National Weather Service Missoula MT 505 PM MDT Mon Aug 31 2026 Note: The experimental wave height forecasts are representative of the mid lake waters and downwind shores. Wave heights may be significantly less on upwind shores. .Tonight...Mostly clear until early morning then becoming mostly cloudy. Lows in the mid 50s. Variable winds up to 10 mph. Waves less than 1 foot. .TUESDAY...Mostly sunny. Highs in the upper 70s. Variable winds up to 10 mph. Waves less than 1 foot. .TUESDAY NIGHT...Mostly cloudy. A slight chance of rain in the evening, then a chance of rain after midnight. Lows in the upper 50s. Variable winds up to 10 mph. Chance of rain 40 percent. Waves less than 1 foot. .WEDNESDAY...Cooler. Rain likely in the morning, then showers likely and a chance of thunderstorms in the afternoon. Some thunderstorms may produce strong gusty winds in the afternoon. Highs in the mid 60s. Variable winds up to 10 mph becoming southwest around 15 mph in the afternoon. Chance of precipitation 70 percent. Waves less than 1 foot.