The City of Evanston uses the Thor Guard Lightning Prediction System to help alert park users to hazardous weather conditions.

The system is located at James Park, the Robert Crown Athletics Fields and the Dempster Street Beach Office. The system is operational seven days a week, from 8:00 a.m. to 10 p.m., mid-March through mid-November.

When a lightning threat is detected:

• The system will give one 15-second horn blast and strobe light flashes
• Park users should clear the area immediately and find appropriate shelter

When the lightning threat has passed:

• The system will give three 5-second horn blasts and the strobe light stops
• Park users can resume all outdoor activities

Caution: 

The Thor Guard System helps assess the conditions. Neither the signal nor the system is intended to guarantee that conditions are safe. If the weather is threatening and no warning signal is heard or seen, use good judgment and clear the park or field. Do not wait for the warning signal to activate.