Weather Planning

Hundreds of outdoor activities are conducted on public properties in Bay City throughout the year. Activities range from small family gatherings to large special events that attract thousands of participants. Typically, the majority of these activities occur during the spring and summer months from May through September. Weather conditions play a significant role in the success of outdoor activities, and severe weather events have the potential to create dangerous and life-threatening conditions. Since severe weather events pose a serious threat to people and property in Michigan each year, and those participating in outdoor activities are particularly at risk, the City has prepared a weather guide to alert park users and special event organizers to the dangers.

The following information is intended to assist those responsible for planning outdoor activities, to anticipate and recognize severe weather events, and to make reasonable decisions on the basis of weather conditions that will insure for the safety of participants.

Severe Thunderstorm Weather Events

The following are examples of weather events associated with severe thunderstorms:
  • Hail
  • Lighting
  • Straight line winds
  • Tornadoes

Severe Weather Event Facts

  • Most severe weather events occur during the warmest and most humid parts of the day, usually during the afternoon and evening.
  • Thunderstorms may produce excessive precipitation, hail, lighting, high winds and tornadoes. All thunderstorms are dangerous!
  • The typical thunderstorm is 15 miles in diameter and lasts for approximately 30 minutes. Mature supercell thunderstorms can last for many hours.
  • Severe thunderstorms are those that produce 1 inch hail or larger and winds 58 miles per hour (mph) or greater, or tornadoes.


  • Lightning occurs in all thunderstorms and is a significant threat to life. Lightning tends to strike the highest object in an area.


  • Hail is an indication of a strong thunderstorm.
  • Large hailstones can fall at speeds faster than 100 mph.
  • Hail can fall for an extended period of time and cause significant damage.

High Winds

  • Strong winds can produce damage equal to that of a tornado.
  • Straight line winds can exceed 100 mph and are responsible for most thunderstorm wind damage.
  • A "downburst," which is a type of straight line wind, can cause damage equivalent to a tornado.


  • The average forward speed of a tornado is 30 mph but may vary from stationary to 70 mph. The strongest tornadoes have rotating winds of more than 250 mph.
  • Tornadoes can occur at any time of the year. Tornadoes are most likely to occur during the warm months between 3 and 9 p.m., but can happen at any time.
  • The average tornado moves from southwest to northeast, but tornadoes have been known to move in any direction.

Safety Recommendations

  • Check weather conditions in advance of your outdoor event or activity.
  • Monitor weather conditions during the event or activity. This can be done visually and by monitoring a local weather station by radio.
  • All weather warnings should be taken seriously! Weather warnings indicate imminent danger to life and property for those in the path of a storm.
  • Respond immediately to any weather alerts or emergency sirens by taking cover in a safe location. Tents, open shelters, sheds, baseball dugouts, bleachers and the underside of bridges are not considered safe shelters. Enclosed buildings are considered safe shelters. Cars and the underside of highway overpasses are not safe shelters for tornadoes. Cars, except for convertibles, are considered safe shelters from lighting.
  • The lightning safety community states that there is no safe place to be outside in a thunderstorm. If outdoors, get inside a suitable shelter or safe vehicle immediately!
  • Suspend activities for 30 minutes after the last observed lightning strike or thunder.
  • If caught outdoors during a thunderstorm and there is no shelter available, find a low spot and stay away from trees, telephone poles, power lines, towers, fences and other tall objects. Crouch down in an open area and if you're with a group of people stay a few feet away from each other.
  • Avoid contact with water features during thunderstorms (lakes, ponds, streams, rivers).
  • If you feel your skin tingle or your hair stand on end, squat low to the ground. Make yourself the smallest target possible. Do not lie down!
  • Avoid using electrical appliances during thunderstorms. Avoid touching anything metal.
  • If someone is struck by lightning call 911 immediately and apply First Aid procedures if you are qualified to do so!

Weather Information/Updates

Weather updates are available from a number of sources including the following: