Protect yourself at the parks: What is Thor Guard and how does it work?

  • Thor Guard, The Hub at Berens Park, Elmhurst, IL

With all the storms the area has seen recently, it’s a good time to remind the community about the Park District’s lightning prediction system, Thor Guard.


The District’s lightning prediction system – Thor Guard -- is located at six District sites:

  • Berens Park
  • Butterfield Park
  • Eldridge Park
  • Plunkett Park
  • Sugar Creek Golf Course
  • Wilder Park (strobe light only, no warning horn).

How it works

Thor Guard sensors measure and analyze the electrostatic field in the atmosphere. The coverage area is a radius of 2.5 miles and the system is 97% accurate within a 2-mile radius.  The system predicts the potential occurrence of lightning 8-20 minutes before it could possibly strike.  The system operates seven days per week, from 8 a.m.-11 p.m. from March through November. When school is in session, the systems at Berens, Plunkett, Butterfield, and Wilder, only operate 3 p.m–11 p.m. Monday – Friday.

What the signals mean

  • A warning horn (strobe light only at Wilder Park) will sound with an uninterrupted 15-second blast and a strobe light will turn on when there is the potential for a lightning strike within the coverage area.  Upon hearing this signal, patrons must immediately seek appropriate shelter.
  • When the system senses that conditions are safe, the horn will sound three short 5-second blasts and the strobe light will turn off.  This horn signals that normal activity may resume.
  • Even if the lightning prediction system does not sound, but weather conditions are threatening, good judgment should prevail and patrons should seek appropriate shelter. Individuals not obeying the warning signal do so at their own risk.

Emergency Tips

  • Patrons should seek shelter inside their vehicles or within a lightning protected building.
  • Patrons should avoid trees, picnic shelters, fences, bicycles, or any other metal objects.
  • Patrons should stay out of and away from water, including pools and showers.
  • Patrons should avoid using electrical appliances including telephones.
  • If you should feel your hair is or is about to stand on end, drop to your knees and place your hands on your knees.  Do not lie flat on the ground.

The public can also sign up for Rainout Line, the Park District’s weather cancellation service, to be up-to-date on weather delays or facility closings. Receive updates by text, email, the Rainout Line App or at our Rainout Line website.