2025-04-30 , updated 2025-04-30
Was the incident caused by an unusual weather event?
Written by: Robert
Keywords: power-grid, civil-protection, readyness
On April 28 at 12:33 p.m. (11:33 BST), a widespread power outage occurred across Spain and Portugal, as well as parts of France. In Spain, major cities such as Madrid and Barcelona were affected, while in Portugal, the capital Lisbon and surrounding areas, as well as the northern and southern regions of the country, experienced disruptions. Power was also cut in southwestern France, but service was restored by mid-afternoon.
The outage impacted hospitals (forcing a switch to emergency power), mobile networks, public transportation systems such as metros and trains, traffic lights, as well as industrial and residential consumers.
Internet connectivity and services was also affected, including global services that rely on Spain’s digital infrastructure, such as content delivery networks
By 10pm local time on Monday, 62% of Spain’s substations were back online (421 of 680).
(image: Spain power consumption drop 2025-04-28, source: www.ree.es)
Disruptions to critical energy infrastructure and power supply should be thoroughly documented to provide regulators and decision-makers with better data to prevent or reduce the likelihood of similar events in the future. At the same time, it is important for grid operators to maintain adequate security and avoid disclosing architectural details that could expose vulnerabilities to potential attackers (e.g., in the case of cyberattacks).
Balancing transparency to learn from incidents like this, while safeguarding infrastructure and reducing vulnerabilities, is key to long-term improvements in resilience.
This note primarily considers the incident through the lens of naturally occurring threats. When a large-scale power outage occurs, one may initially suspect Carrington-type events or geomagnetic storms. However, no reports have indicated unusually strong ground currents around the time of the incident. Could there have been another geophysical cause?
So far, official responses regarding the cause of the outage have been limited. According to the Portuguese Prime Minister, the incident originated in Spain. Spanish media initially cited the Portuguese grid operator REN as attributing the cause to a “rare atmospheric phenomenon,” but REN later denied having made such a statement.
T. Engelaar, Managing Director at Neara, a software provider to energy utilities, was quoted as saying, “Due to the variation of the temperature, the parameters of the conductor change slightly.” Although the statement is vague, one interpretation is that sudden or extreme temperature changes may have impacted conductivity, AC frequency, or supply-demand control systems in a way that triggered an automatic shutdown.
The outage may have resulted from control systems failing to register a minor issue that later cascaded into a larger system failure. However, no further information has been released by the grid operators.
This is a well known phenomenon for engineers. There are mainly two types of longitunal waves, which can be caused by certain wind pattern:
According to historical data, temperatures in Madrid on April 28 ranged from 17–22 °C (April/May average: 15 °C), with winds at 2–4 m/s. In Lisbon, temperatures ranged from 15–25 °C (April/May average: 16 °C). However, some regions in Spain reportedly experienced unusually high temperatures on Monday. Even though historical data do not indicate extreme weather, could rapidly rising warm air have caused localized strong winds that disrupted power lines?
Geomagnetic storms can induce ground currents that damage transformers and other electrical components. However, no geomagnetic storms were registered during the relevant period.
In meteorology and upper atmospheric science, gravity waves are well-studied. These waves are typically generated by weather systems like cyclones or hurricanes. They propagate upward through the atmosphere, initially with low amplitude, which increases with altitude as the air thins, eventually dissipating and influencing upper atmospheric circulation.
To date, gravity waves have not been seriously considered as a cause of power outages. Only one source has mentioned this possibility.
Could gravity waves also be generated by extreme temperature differences, if such conditions were present in parts of Spain on Monday? Could the characteristic oscillations or wave-length of gravity waves interact with the harmonics of the length of long distance power lines in such a way as to induce amplification or positive feedback on power line waves?
While Spanish authorities have denied cyberattacks as a cause, the current geopolitical climate warrants continued scrutiny. Several factors support further investigation:
However, without concrete evidence, cyber attacks remain a speculative cause. Investigation continues to focus on technical and environmental factors.
The exact cause of the April 28 power outage remains unclear. Reports from grid operators lack detail and are not corroborated by independent experts in electrical engineering or geophysics. More thorough investigation and transparency are needed to learn from incidents like this and to ensure power systems are better prepared for a wide range of internal and external threats.