Be Ready for Severe Thunderstorms
Severe weather has the potential to occur year-round in St. Louis. Thunderstorms can bring strong winds, hail, lightning and flash flooding, while winter storms may include sleet, freezing rain, ice and heavy snow fall.
By monitoring weather conditions and preparing in advance, many of the inconveniences and deadly impacts of winter weather can be avoided.
Understanding the Risk
Severe weather in the St. Louis region can develop quickly. WashU Emergency Management wants you to be prepared and know how to act when severe or destructive thunderstorms are in the forecast.
Watches vs. Warnings
- Severe Thunderstorm Watch: Be alert. Conditions are favorable for a watch if 1″ hail or wind gust greater than 58 mph are possible.
- Severe Thunderstorm Warning: Take action now. A severe thunderstorm warning has been detected by radar.
- Destructive Thunderstorm Warning: Issued for extremely dangerous storms with winds over 80 mph or large hail. Treat it like a tornado warning.
Get Alerts from Multiple Sources
Outdoor warning sirens are intended for people outdoors and may not be heard inside buildings. Don’t rely on sirens alone. Use multiple reliable sources:
- 📲 WashU Safe App — emergency alerts, resources, and safety features
- 📻 NOAA Weather Radio — direct alerts from the National Weather Service
- 📺 TV and local news apps — continuous weather updates
- 📡 Wireless Emergency Alerts — from your cell carrier
Download the WashU Safe App
The WashU Safe app is your mobile hub for emergency alerts and preparedness resources. Get real-time warnings and protective action messages straight to your phone.
“Destructive” and “Considerable” Damage Threat Categories
We developed three categories of damage threat for Severe Thunderstorm Warnings. The categories, in order of highest to lowest damage threat, are destructive, considerable, and base. These tags and additional messaging are designed to promote immediate action, based on the threats.
- The criteria for a destructive damage threat is at least 2.75 inch diameter (baseball-sized) hail and/or 80 mph thunderstorm winds. Warnings with this tag will automatically activate a Wireless Emergency Alert (WEA) on smartphones within the warned area.
- The criteria for a considerable damage threat is at least 1.75 inch diameter (golf ball-sized) hail and/or 70 mph thunderstorm winds. This will not activate a WEA.
- The criteria for a baseline or “base” severe thunderstorm warning remains unchanged, 1.00 inch (quarter-sized) hail and/or 58 mph thunderstorm winds. This will not activate a WEA. When no damage threat tag is present, damage is expected to be at the base level.
On average, only 10 percent of all severe thunderstorms reach the destructive category each year, nationwide. Most of these storms are damaging wind events such as derechoes and some of the larger, more intense thunderstorms, called “Supercell” storms that can typically produce very large hail in their path. The new destructive thunderstorm category conveys to the public urgent action is needed, a life-threatening event is occurring and may cause substantial damage to property. Storms categorized as destructive will trigger a WEA to your cell phone.
How to prepare before it happens
- Keep an NOAA weather radio at a location that will allow alerts to be heard by occupants in the work area.
- Monitor the weather anytime there is a potential for severe weather.
- For winter weather, maintain an emergency kit that contains adequate clothing and blankets to keep warm.
What to do when it happens
- Stay updated with changing weather conditions.
- Stay inside during the storm.
- Minimize travel under difficult conditions.
- During thunderstorms, avoid contact with electrical equipment, corded phones/devices and plumbing.
- Walk carefully during snowy, icy conditions.
- Report any power losses to WashU Police (Danforth, West and North campuses) at 314-935-5555 or Protective Services (Medical School) at 314-362-4357.
What to do right after it happens
- Stay away from storm-damaged areas, including downed power lines.
- Report any damages to WashU Police or Protective Services.
- Restock any emergency supplies.