Watching a developing storm may be too late to protect patrons at golf courses, parks, pools, ball fields, and other outdoor sites. Lightning can strike far in advance of storm clouds or well after a storm seems to pass. Thor Guard Model L150 monitors intensity of electrostatic energy associated with lightning activity and predicts the probability of a first strike within a certain time and within a defined area up to 5 mi. in diameter. Gives a critical Red Alert for 8 to 20 mins. in advance of a potential strike so that officials can advise patrons to seek shelter. Activity detector subsequently advises projected time until activities can resume safely. Console features an easy-to-read, color vacuum fluorescent display; a field-collapse-count indicator that shows lightning discharges during the storm; 3 warning levels of electrical activity (Caution, Warning, Red Alert) plus All Clear; automatic monitoring for bolt-out-of-the-blue conditions; auto/manual control for either monitored or unmonitored operation; and RS232 port that interfaces with Thor Guard Weathers Internet-based, weather-subscription service.