Once a thunderstorm is present, there is a risk of lightning and the lightning is very unpredictable. To predict exactly when lightning will strike, or even the exact place that will be hit is (and probably will for a very long time be) impossible. There are certain detectors of electric field which can warn against imminent lightning, but they are not accurate enough to determine when and where will lightning strike next. However, there are measures that can effectively reduce the risk of damage to people and property
A useful device to warn people when lightning is in the vicinity is a so-called personal lightning detector. It is a 15x8x3cm box that detects electromagnetic waves that are produced by lightning and if it detects any it makes a beep and shows the approximate distance of the strike in miles from the detector. There are several types of personal lightning detector ranging in price from approximately £20 to £150. The detector however needs to be switched on for it to detect lightning so the weather forecast still needs to be monitored for the possibility of thunderstorms and if thunderstorms are possible, switch the detector on (a daily thunderstorm forecast is produced www.estofex.org which includes a map of lightning probability. I’d recommend to switch on your lightning detector anytime that you are within the 15% line). Such a personal lightning detector can either be plugged in to the wall or it is possible to insert a classic AA battery (or other battery depending on the model) and take it out with you. If there is a strike in the vicinity of up to approximately 50 miles the detector will alert you and show the range in distance at which the lightning was detected. Sometimes it can, however, suffer strong interference which can make it beep even if there is no lightning. This most often occurs if you switch on a TV, if you are in a car with an engine running and sometimes even if you switch on your lights at home. It is therefore best to keep it in a place away from other appliances and not use it in a car. If the detector shows lightning detected 12 miles away or closer I would recommend not to be outdoors or seek shelter and wait at least 15 minutes after the detector stops detecting lightning less than 12 miles away.
While it’s much more dangerous to be outdoors than inside during a thunderstorm it’s not totally safe even indoors, especially if the building has no lightning rods installed. If the storm is less than 10 miles away and you are at home I would recommend to manually disconnect the electricity (switch off the mains switch, normally located at or inside the fuse box). This protects your home appliances should lightning strike the mains power cables and get into your house along the electrical wiring. If you go on a holiday, especially during the summer months when thunderstorms occur most often, I would recommend disconnecting all the devices that can be disconnected (TV, computers, routers, radios, etc.). If you do not have a device that you can not disconnect (fridge, freezer, etc.), I recommend buying special “lightning protection”, which is a device that is plugged in between the socket and the appliance and in case lightning strikes the electrical mains outside the protection would act like a fuse and would not let the high voltage current damage your appliance. In this case the lightning protection gets damaged and hence your fridge would stop working, but I would say it’s much better to return home and find bad smelly food in your fridge and buy a new lightning protection for less than £10 than to find bad food inside a broken fridge that needs to be replaced. Another way how lightning can get inside a house is along water pipes. Therefore, I would not recommend using the sink, washbasin, the bathtub, or even avoid being at the toilet as much as possible during a thunderstorm. The safest place to be inside a house during a thunderstorm is away from doors and windows, any electrical appliances and away from any pipes that lead outside. Best place would be to stay in an inside room with no outer doors or windows. Chimneys have also been known, on occasions, to be a way how lightning can get inside a house. Therefore, avoid sitting next to a fireplace. To maximize your protection you could wrap inside a blanket which would act as an insulator and should, to some degree, prevent lightning to hit you if it indeed entered your house. If you want to be in a place that is as safe as possible during a thunderstorm (regarding the risk of lightning strike) you need to find a place that would act like a “Faradays Cage” and would have a metal frame that would guide the lightning current around you away into the ground. An example of such a Faradays Cage is a car (not a convertible! The soft roof of convertibles is not conductive and hence doesn’t act like a Faradays Cage!). Other means of transport often act like a Faradays Cage since they have a metal frame or a frame made from some conductive material (e.g. buses, trains, airplanes, etc.).
If you find yourself far from any shelters, for example in rural areas or outside in nature you can still do something to reduce the chance of being struck. Places to avoid if caught outside are tall solitary trees or stones, tops of hills and any largely open spaces. Swimming in a sea, lake or river is very dangerous if a thunderstorm is nearby. Even if lightning does not strike you directly, if it strikes the water where you are swimming up to a mile away you would feel the electric shock which may cause temporary loss of consciousness leading to drowning. So if you do get caught in a rural location find the lowest place in the vicinity away from any tall trees, buildings (unless you can go inside them) or other objects. It may be tempting to go and hide from the rain or hail under a tree, but if you do so you are in much greater danger of being struck. The best thing to do would be to find a ditch and crouch in it, but watch out for any flash floods as ditches can fill quickly with water if the rain is very heavy. If you are caught in a park or a forest you are actually in a safer place then if you were in an open field, as long as you avoid the tallest trees. If the storm is strong and accompanied by wind gusts there is of course a danger of falling trees or branches in a forest. If you get caught in the mountains, definitely leave the highest ridge (if there is time and it’s not a dangerous route) and try to get into a valley or at least away from the highest stones and ridges. Being just below the ridge is not safe as well since if lightning hits the top a very large electric potential forms which can cause electric shock solely due to different locations of your feet (it’s called step charge).
To conclude, there is no place that would be 100% safe from being hit by lightning, but if you follow the above advice you will greatly reduce the risk of injuries or damage to property. While the chance of being hit by lightning is still very small in comparison to other risks that threaten us in our everyday life there is no excuse not to follow these safety procedures. The people who are struck by lightning often did not take appropriate action when near a thunderstorm. It’s questionable how high the proportion of people that was struck knew about the presence of a thunderstorm nearby, but if everyone was aware of thunderstorms in their vicinity and always took precautionary action the number of injuries and fatalities related to lightning could still be greatly reduced. And if you are terrified of lightning (astrapophobia) you can always do the opposite of stormchasing. By learning about thunderstorms and weather in general you can learn what conditions are favorable for thunderstorms and if storms do develop or are forecast just drive into a location where the chance of storm development is zero or the lowest. I did this a few times when observing eclipses of the Sun and while finding a place to be cloud free is difficult (but easier than stormchasing), simply avoiding storms is really easy and I can be confident that by driving to a different location I could avoid all lightning (unless there is a large squall-line that would cross the whole of the UK, but such a case would be extremely rare).