If you hear thunder, you should move to an indoor location immediately. Avoid using electrical appliances and only use the telephone in emergencies. If a safe, enclosed shelter is not available and you are caught outside during a lightning storm, get away from water, metal objects and tall trees. Crouch low to the ground. Excessive rainfall, especially when combined with rapid snowmelt, can create dangerous flooding.
Thunderstorms produce flash flooding when very heavy rain falls in a short period of time.
Flash floods occur quickly and inundate streets with rapidly moving water. You should never walk or drive a car into the flood waters. Instead, turn around or abandon your car and move to higher ground. Even six inches of fast moving water can knock an adult off their feet and two feet of water will carry away most automobiles. Tornadoes are infrequent in Montana, but they can occur during a severe thunderstorm.