SXUS45 KMSO 212330 RECGPI Recreation Forecast for Flathead Lake National Weather Service Missoula MT 505 PM MDT Mon Sep 21 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. Lows in the mid 50s. Variable winds up to 10 mph. Waves less than 1 foot. .TUESDAY...Mostly sunny. Highs around 70 . Variable winds up to 10 mph. Waves less than 1 foot. .TUESDAY NIGHT...Mostly cloudy in the evening then clearing. Lows in the mid 50s. Variable winds up to 10 mph. Waves less than 1 foot. .WEDNESDAY...Sunny. Highs in the upper 60s. Variable winds up to 10 mph. Waves less than 1 foot.