Two men died in the North Karelia municipality of Juuka on Friday, when an electric charge caused by a lightning strike conducted through nearby wet soil to their bodies, Finnish police report.
The Finnish Medical Society Duodecim says lightning strikes kill between one and two people each year in Finland. In much the same way as an electric shock, the effects of a lightning strike can cause burns or seizures. In worst cases, the electric charge created by the natural phenomenon can bring about cardiac arrest or stop a person's breathing.
The shock wave that results from the lightning flash can also damage the ears or throw the victim, breaking bones.
Moisture improves the conductivity of the electric current that creates lightning, so a wet location will cause a more dangerous charge to channel through the body than a dry one.
Duodecim recommends that people who have felt the effects of a lightning strike in their body be brought to treatment immediately. Even if no wounds are visible, the charge may have caused internal bodily damage.
Find shelter in a building or a car, if possible
If thunder can be heard at all, then there is lightning. If you can hear thunder less than 30 seconds after seeing lightning, it is close enough to pose a threat.
At this point at the latest, experts recommend finding shelter.
The safest place during a lightning storm is inside a building or a vehicle. If this isn't possible, the Finnish Meteorological Institute (FMI) recommends crouching down and staying low. Do not use an umbrella, as they can act as a conduit.
FMI also advises people caught in a lightning storm to stay away from high places and water. Boaters should get off the water onto the shore, if possible.
Rubber boats will not protect you from a direct lightning strike, but they will safeguard your body from "step potential" – the ground current that races towards a lightning strike and sometimes chooses nearby humans as better conductors.
While inside during a lightning storm, avoid using electric devices and stay away from water pipes and fireplaces.
The risk of being hit by lightning remains for up to 30 minutes after the last observed lightning or thunder strike in the area, so do not go back outside until this period of time has passed.
Edit at 1:05 pm: The FMI does not recommend that people take shelter near a tree, as the original Yle story in Finnish said. It instead advises people caught out in the open to crouch and stay low.