Lightning data has become a decision-making tool for building operators, networks, insurers, and maintenance teams. However, a high number alone does not dictate the protection to be installed. It is essential to distinguish between what the network has detected, what the standard requires to be calculated, and what the event actually means for a given site. This rigor is indispensable, in Europe as well as in Africa, America, and Asia.
Vaisala Xweather's 2025 annual report indicates that its network recorded 252 million lightning strikes in the United States, a 20% increase over 2024, and presents this year as the most active in eight years (Vaisala, published in January 2026). This data update should not be interpreted as a simple ranking: it explains why the quality of the monitoring, the terminology, and the local context are crucial.
What a lightning detection network measures
A lightning detection network is a set of sensors and algorithms that locate and characterize electrical events in the atmosphere. Depending on the technology, the results may count lightning strikes, flashes, impacts, or discharges; therefore, it is always necessary to read the definition associated with the figure cited before comparing two reports.
The figure of 252 million reported by Vaisala relates to events in its 2025 financial statements for the United States. It reflects large-scale activity; however, it does not automatically constitute a risk assessment for an individual building, factory, or site. A protection decision requires data tailored to the specific location, structure, and incoming networks.
- The observation period and geographical area must be known.
- The type of event counted must be specified before any comparison.
- National data does not replace localized data or risk analysis.
Ng and Nsg: two terms not to be confused
Ground lightning density (Ng) is the annual number of ground lightning strikes per square kilometer. It is used in approaches based on IEC 62305, particularly to assess the number of hazardous events likely to affect a structure. Ng is not obsolete: it is the relevant term in this normative context.
The term Nsg refers here to a density of activity in clouds or above the ground, derived from Strike Radar. It serves a purpose of monitoring and understanding storm activity; it should not be presented as a direct substitute for Ng in risk assessment calculations. Therefore, using the correct term avoids design errors and makes the documentation clear to all rodholders.
- Ng : ground lightning strike data used in IEC 62305 risk analyses.
- Nsg : data from Strike Radar to describe activity in the clouds or above the ground.
- Event detected : localized and dated information that must be interpreted with its technical context.
What can we deduce from the 252 million events?
We can deduce that measured electrical activity was particularly high within the perimeter and according to the method described in the report; however, we cannot conclude, without further study, that every structure requires the same level of protection. The answer depends on the building's geometry, its environment, its occupants, its networks, and the assessed level of loss.
IEC 62305-2 organizes risk assessment around several sources of damage: impact on the structure, impact on nearby areas, impact on an incoming line, or impact near a line. Furthermore, it distinguishes between injuries to living beings, physical damage, and failures of internal networks. This method therefore links exposure data to concrete consequences, rather than drawing conclusions based solely on a single meter reading.
- Identify the site, its use, its networks and the people potentially exposed.
- Use a location-appropriate Ng value in risk assessment.
- Examine the scenarios of direct impact, near impact and overvoltages through the lines.
- Choose the protection measures and retain the justification for the level chosen.
Why the detected events remain useful to the field
Event data does not replace analysis; however, it can improve operations. For example, it helps correlate a reported disruption, equipment downtime, or inspection with a documented storm event. This information becomes particularly useful for multi-site facilities, isolated infrastructures, and installations where teams are not permanently present.
Strike Radar is designed for recording events and providing data such as Nsg. It should not be confused with Sky Sentinel, which is for real-time alerts. The documentation associated with an event can then be added to the facility's file to determine whether an inspection, measurement, or corrective action is required.
- Match the site, date and time of the event with the available information.
- Check the condition of critical equipment and surge protection if the scenario warrants it.
- Keep track of field findings, measurements and decisions taken.
From map to protection plan: the complete process
A mapping data point or an alert is only the first step. External protection captures, conducts, and disperses lightning current; internal protection reduces the effects of overvoltage on networks and equipment. Furthermore, Equipotential Spark Gap and grounding must be considered in conjunction with other system components, as a fault can originate from a nearby strike or from an incoming line without any visible impact on the roof.
For buildings equipped with lightning rods, the choice of an early streamer emission (ESE) lightning rod is determined by the design and applicable project standards. The correct term in French is ESE. It is never a matter of deducing a radius, model, or level of protection from a general statistical analysis: these choices are based on the study, the technical documentation, and the site requirements.
- Assess the risk before sizing.
- Coordinate the external system, surge arresters and grounding connections.
- Plan for initial, periodic and, where necessary, exceptional checks.
Organizing data over time
An installation changes along with the building: expansion, new equipment, line modifications, component replacement, or a change of use. Therefore, the record must remain active. LPS Manager centralizes installation information, schedules inspections, and provides access to keraunic reports and lightning strike certificates available through Strike Radar.
LPS Manager does not directly produce NSG. Its role is to structure the monitoring, while Strike Radar provides the NSG data and associated documentation. This separation is useful: it keeps the difference between the measurement or report, the technical decision, and the action taken in the field clearly visible.
- Retain the risk analysis and plans as a starting point.
- Attach event and control reports to the correct site.
- Follow up on corrective actions until their verified closure.
Conclusion: Transforming a number into a defensible decision
The 252 million events recorded by Vaisala in 2025 illustrate the growing importance of detection data. However, reliable protection begins with the right definitions: Ng for ground lightning density in the IEC 62305 analysis, and Nsg for Strike Radar data above ground or in clouds. Next, a site study links exposure to potential consequences and appropriate measures. Finally, within the lpsplatform.com, Strike Radar, Sky Sentinel, and LPS Manager can complement this approach with recording, alerting, and traceability, without ever replacing professional design or verification.
