© Yuki ShibataLightning strikes behind the control tower at Haneda Airport in Tokyo on July 6.
Tokyoites may be safer in thunderstorms than people in rural areas because lightning tends to hit tall buildings. But as summer temperatures have risen, the threat from lightning strikes has also increased, particularly in the capital.
On the evening of July 22, lightning struck the headquarters of Metrol Inc., a precision equipment manufacturer in Tachikawa in the Tama region of western Tokyo.
The company's fax machine malfunctioned, and some orders could not be placed or received.
After the machine was fixed, another lightning bolt struck on July 24, knocking out the fax machine again.
The lightning storm in the neighborhood prevented a technician from immediately going to the site to repair the machine.
Lightning also zapped Metrol's factory, causing machines to break down and settings to change on their own.
The company plans to spend several hundred thousand yen to install lightning protection breakers on its major machinery.
"Lately, we have been having thunderstorms every evening," Metrol President Takuji Matsuhashi said. "If a machine breaks down, the damage could run into the millions or tens of millions of yen. We have to change our conventional countermeasures at once."
According to Franklin Japan, a lightning-observation meteorological company in Sagamihara, Kanagawa Prefecture, the number of lightning strikes in the Kanto region, which consists of Tokyo and six prefectures, reached 165,000 in July and August, about 1.6 times the average number.
In Tokyo, the number of lightning strikes was about 3.3 times higher than normal, Saitama Prefecture about 2.8 times higher than normal, and Ibaraki Prefecture about 1.8 times higher than normal.
Cumulonimbus clouds, or thunderclouds, tend to develop when temperatures are high and moist air flows through the sky due to a weak overhang of high pressure. Such conditions were more common this summer, leading to the increase in lightning strikes, Franklin Japan said.
According to the company, electronic equipment can break down due to a phenomenon called "induced lightning," in which lightning travels through electric wires and enters indoor areas.
At the Omiya Bonsai Art Museum in Saitama city, air conditioners failed during a lightning storm on the night of Aug. 7. Lightning hit the circuit boards of six outdoor air conditioning units, and the museum was forced to suspend operations until Aug. 24.
According to Shohei Kato, a professor emeritus of electrical, electronic and communications engineering at Toyo University and an expert on lightning, induced lightning is not the only danger to indoor equipment.
Lightning strikes near buildings can also generate powerful electromagnetic waves that penetrate the interior of buildings. These waves can cause home appliances and electronic equipment to malfunction.
"Information and communications equipment, such as landline telephones, fax machines and internet devices, are particularly at risk," Kato said.
Preventative measures include unplugging the equipment before a storm, he said.
He also advises people, especially in rural areas, to take precautions against thunderstorms.
In April, lightning struck a high school in Miyazaki Prefecture during a soccer practice, sending 18 students to a hospital.
"In wide areas where there are no tall objects around, there is a danger of a direct hit," Kato said.
He said if you hear thunder, you should seek shelter in a building or car and avoid getting close to tall objects, such as trees or utility poles.
Lightning that hits a tree or pole can fly through the air and send an electric current to nearby people or objects. This is called "side strike lightning," he said.
And if you are inside a house, it is safer to stay in the center of the room away from electronic devices, he said.
"Lightning strikes are increasing," Kato said. "Nowadays, cumulonimbus clouds form over wide areas, and thunderstorms with heavy downpours can occur several times every few hours.
"Effective countermeasures against lightning are currently difficult, but we must at least be aware of lightning strike information to avoid human casualties."
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