| Primary sensing variable | Vertical atmospheric electric field, commonly expressed in volts per metre (V/m) or kilovolts per metre (kV/m). | Storm development can be tracked by observing field strength, polarity changes, and rapid fluctuations near the ground. | The field is affected by terrain, buildings, overhead power lines, dust, and local electrical equipment. |
| Fair-weather reference | Near-surface fair-weather electric fields are typically around 100–150 V/m downward, although local conditions vary. | Provides a baseline against which storm-related changes can be compared. | A baseline is not universal; coastal, urban, mountainous, and polluted environments may produce different readings. |
| Storm-field behavior | Thunderstorm electric fields can rise to the kV/m range and may change rapidly as charge regions develop. | Increasing field magnitude or rapid field reversals can indicate that a charged storm is approaching or intensifying. | A high field does not identify the exact lightning location or guarantee that a strike will occur at a particular site. |
| Real-time measurement | Continuous monitoring Measurements can be sampled repeatedly, from seconds to sub-second intervals depending on the device design. | Frequent updates allow alerts to be triggered from trends instead of relying only on occasional weather observations. | Sampling rate, filtering, calibration, and alarm logic differ between systems. |
| Storm approach indication | Rising or increasingly variable electric-field values may occur before nearby lightning, but timing is not fixed. | Trend analysis can provide an earlier warning than waiting for audible thunder or a visible flash. | Warning lead time may range from very short to several minutes and cannot be guaranteed for every storm. |
| Lightning-distance context | Thunder can normally be heard from lightning several kilometres away; distant lightning may be visible or detected farther away than it can be heard. | Sensor alerts can support decisions to suspend outdoor work before a storm appears overhead. | Electric-field sensors alone generally estimate local atmospheric electrical conditions rather than giving a precise strike-distance measurement. |
| Detection of nearby electrical activity | Rapid field changes may accompany lightning initiation, nearby discharges, or strong charge rearrangement. | Fast changes can be used as a trigger for immediate warnings in exposed locations. | Short-range field changes may also be caused by switching equipment, vehicles, fences, or other electrical disturbances. |
| Alert decision method | Configurable thresholds Common inputs include absolute field strength, rate of change, persistence, and multiple alarm levels. | Different sites can use pre-alert, warning, and all-clear stages suited to their risk tolerance. | Thresholds should be validated locally because one fixed value is not appropriate for every climate or installation. |
| Geographic coverage | Local-site coverage Best suited to protecting a defined area around the installed sensor. | Works independently of cellular or internet-based regional lightning maps for local warning decisions. | A single sensor cannot provide reliable global storm tracking; wide-area coverage requires a distributed network or additional data sources. |
| Sensor placement | Open, unobstructed locations generally provide more representative atmospheric measurements than areas surrounded by tall structures. | Correct placement improves signal quality and reduces shielding and distortion. | Nearby metal structures, power systems, trees, and overhead cables can distort the measured field. |
| Weather compatibility | Electric-field sensing can operate during daylight, darkness, cloud cover, and rain. | Unlike optical-only observation, it does not require a visible lightning flash or clear line of sight. | Water, salt deposits, dust, ice, and contamination can affect sensor performance and require maintenance. |
| Recommended safety response | Use with a safety plan When a warning is issued, move people to a substantial enclosed building or a hard-topped enclosed vehicle. | Combining automatic alerts with clear evacuation procedures reduces exposure during rapidly changing storms. | Do not treat an all-clear as proof that lightning risk has ended; continue monitoring and follow local emergency guidance. |
| 30-minute safety principle | Wait at least 30 minutes after the last thunder before resuming outdoor activities; thunder means lightning is close enough to be a hazard. | Provides a simple operational rule when sensor readings, forecasts, or visual observations are uncertain. | This is a conservative safety guideline, not a measurement of exact storm distance. |
| Best-use environments | Construction sites, sports fields, outdoor events, farms, ports, utilities, campuses, and remote work areas. | Supports rapid notification where people may be dispersed and normal weather observation is difficult. | High-risk operations still require trained personnel, emergency communication, and formal weather procedures. |
| Overall safety value | Early local awareness | Provides continuous, site-specific information that can complement weather forecasts, radar, satellite data, and regional lightning networks. | No single detection method can predict every lightning strike; layered monitoring and prompt sheltering remain essential. |