A dangerous corridor of fast-moving thunderstorms is bearing down on western and central Montana Thursday afternoon and evening, with authorities warning residents from Grangeville south through Lost Trail, Deer Lodge, and toward Helena to take immediate action before conditions deteriorate.
The storm threat begins at 1 PM MDT and is expected to persist through overnight hours and into Saturday morning — a window that leaves little time for those caught unprepared outdoors.
WHY THESE STORMS ARE ESPECIALLY DANGEROUS
What makes this particular setup alarming is not just the intensity of individual storms — it is how fast they will move. Forecasters say storm motion will track from southwest to northeast at 45 to 55 mph, meaning a storm that appears distant can be overhead within minutes. Wind gusts of up to 50 mph, small hail, frequent cloud-to-ground lightning, and locally heavy rain are all on the table with any storm that develops.
The most significant threat is expected east of the Continental Divide, where surface instability is less likely to be capped through the afternoon hours. Areas along the Flint Creek Range terrain carry a particularly elevated risk for the strongest wind gusts.
STORM PROBABILITY BY LOCATION
South of Lost Trail: 54%
Helena: 33%
Butte: 24%
Hamilton: 19%
Dillon: 13%
Missoula / Grangeville: 9%
Salmon: 3%
WHAT YOU NEED TO DO RIGHT NOW
Anyone with outdoor plans in the affected corridor — hikers, campers, construction workers, and event organizers — should move all activities indoors or reschedule before 1 PM MDT. Authorities stress that once thunder is audible, it is already too late to safely relocate.
The threat does not end at sunset. Storm activity may carry through overnight hours, meaning lightning and damaging winds remain a hazard well into the early morning hours of Saturday, June 27.
If you hear thunder, go inside immediately and stay sheltered until the threat has fully cleared your area. Do not wait to see the storm — by the time it is visible, you may have no time to reach safety.
