It seems like it's always a specific season here in Montana. Be that mud season, hunting season, boating season, ski season, fire season or even pumpkin spice latte season. May is right around the corner and that means it's almost severe weather season for the Treasure State.
Right about when temperatures really start warming up and outdoor activity ramps up, so do the thunderstorms. May in particular is a time when severe weather fires up quickly.
This is because of increasing spring warmth, clashing with stronger low pressures and still cold upper-level air. As air warms it becomes more buoyant and unstable. Add an increase of moisture to the atmosphere in spring, and given the right circumstances, severe thunderstorms increase in possibility.
A thunderstorm is considered severe if it produces hail the size of a quarter or greater, has wind of 58mph or greater, and/or produces a tornado.
Montana averages about 9 tornadoes per year. Typically there is a greater likelihood of a tornado farther east in Montana.
The number of severe thunderstorms more or less also increases the farther east in the state you go. This is because thunderstorm formation is enhanced by the potential lift provided by mountains. Storms get their start over the higher terrain and then intensify as they move over the plains. For example, this is why Billings gets significant hail events after thunderstorms develop over the Beartooth Mountains and intensify as they cross over into the plains.
So as the weather starts heating up, remember 'tis the season for severe thunderstorms.
