Northwest Montana

Issued: 09/07/2026 7:35 p.m. MDT

Tonight...Rain likely with patchy fog. Snow level near 7500 feet. Lows in the 40s with lower 40s around 5000 feet. Light wind except ridge top winds west 10 to 15 mph.

Tuesday…Patchy fog through mid morning otherwise mostly cloudy with scattered showers in the morning then variable clouds in the afternoon with isolated showers. Warmer with highs in the lower 60s to lower 70s with lower 50s around 5000 feet. Afternoon west to southwest wind 5 to 15 mph with gusts to 20 mph along portions of Lake Koocanusa and across ridge tops.

Tuesday night…Partly cloudy in the evening then fair skies except for areas of fog and low clouds developing in the valleys after midnight. Fog could become locally dense. Lows in the mid 30s to mid 40s except upper 40s in thermal belts on slopes and hillsides with mid 40s around 5000 feet. Light wind.

Wednesday...Areas of fog and low clouds in the valleys through mid morning otherwise mostly sunny with a few afternoon clouds and warmer. Fog may be locally dense in the morning. Highs in the 70s to near 80 with near 60 around 5000 feet. Afternoon southwest wind 5 to 15 mph with gusts to 20 mph along portions of Lake Koocanusa and across ridge tops.

Extended Outlook(Thursday through Monday):

Thursday...Areas of late night through mid morning valley fog and low clouds otherwise dry and warm. Lows in the mid 30s to mid 40s with near 50 in thermal belts on slopes, hillsides and around 5000 feet. Highs in the 70s with near 60 around 5000 feet.

Friday...Cooler and locally breezy with a chance of late day showers and thunderstorms. Lows in the 40s with upper 40s around 5000 feet. Highs in the 60s with lower 50s around 5000 feet.

Saturday and Sunday...Cool and locally breezy with a chance of valley rain showers and mountain snow showers. Lows in the mid 30s to mid 40s with mid 30s around 5000 feet. Highs in the mid 50s to mid 60s with mid 40s around 5000 feet.

Monday...Areas of late night and morning valley fog, frost and low clouds otherwise dry and seasonable. Lows in the 30s except locally upper 20s colder valleys with near 40 around 5000 feet. Highs in the 60s to near 70 with near 50 around 5000 feet.

In-Depth Weather Discussion for Northwest Montana/North Idaho/Northern Rockies 

Issued 09/06/2026 8:10 p.m. MDT / 7:10 p.m. PDT

SHORT TERM (SUNDAY NIGHT THROUGH TUESDAY):       

      Fairly active Sunday late afternoon and evening across our region as a shortwave approaches from the south moving around the upper level low that is currently spinning across North Central Oregon and South Central Washington. The lift and instability associated with this shortwave has kicked off several strong thunderstorms initially developing across Northwest Montana but in the last couple of hours North Idaho as well as Northeast Washington have seen a rapid development of convection. Thunderstorms will continue to develop into the evening hours as the shortwave passes through then will transition to more of a stable steady rainfall as instability wanes and the forcing comes from a deformation axis of convergence on the backside of the departing upper level low. Most areas should see some very beneficial rainfall amounts with amounts ranging from around 0.50 inches all the way up to possibly 2.00 inches in some areas. While this won't be a fire season ending rainfall it will put a large dent in what has been an extremely long duration fire season thanks to the lack of snow last winter, the abundance of winter and early spring rainfall and, for much of North Idaho and Northwest Montana a record dry summer. The upper level low will pull away by Tuesday morning but some shallow instability and a weak vort max dropping southeast on the backside of the departing upper level low may kick off a couple of low topped showers Tuesday afternoon mainly across Northwest Montana. Temperatures will be very cool on Monday with widespread rainfall and many North Idaho valleys as well as most Lincoln County and far northern Sanders County valleys in Northwest Montana likely staying in the 50s all day. Snow will really not be an issue as this is not a very cold system and snow levels look to stay around 7000 feet or higher. Could see some valley fog and low stratus develop Tuesday morning especially across North Idaho valleys which will likely clear out faster than those in Northwest Montana.                

LONG TERM (TUESDAY NIGHT THROUGH SUNDAY): 

     Upper level ridging will quickly amplify once again across the Northern Rockies by Wednesday and Thursday bringing a dry and stable airmass but with all of the recent rainfall by this time, the lowering sun angle and shorter days high temperatures will likely not rise into the 80s although can't rule out some of our warmest Northwest Montana valleys (ie: Libby, Thompson Falls, Plains, etc) seeing 80 or a little warmer again especially if we get some breezes in the afternoon to mix the warmer air aloft to the surface. By late Thursday a cool upper level trough or in some models a closed low will be dropping down the British Columbia coastline and swing inland across Washington state and into the Northern Rockies by Friday and Saturday before exiting on Sunday. This system has not shown a lot of consistency as far as precipitation amounts and models are having a hard time resolving this feature. It could be that this system may end up being a rather dynamic system with some upper level jet support and may end up overperforming but will have to wait and see. This will likely be a colder system and snow will likely fall down to around 6000 feet or perhaps a bit lower with it but again still a bit too early to make predictions on that. Some valleys are likely to see frost during the late night and early morning hours this week on Wednesday and Thursday mornings and perhaps again by Sunday morning if clouds clear out in time. The combination of warm days and the upcoming cool nights and periodic precipitation chances should begin the autumnal color show put on by our trees. The seasons are changing.