Is it possible to heat water to boiling point using lightning rods? This is just a thought i had when i was in the shower. Is it possible to heat water to boiling point using resistors in a circuit that diverts electric current from lightning strikes to ground? Sure there are regulations that say you can only have a maximum of 25 ohms of resistance when you set up a grounding circuit for lightning protection but i think that is for residencial areas. What if the circuit is purpose-built to provide a path of least resistance for lightning to heat up water just like how an electric kettle would?
I am leaning towards the possibility that it won't be hot enough, but i think the other possibilities are it will be hot enough but only for a short period of time that not enough heat energy can be absorbed by the water, or a steam explosion
I would like to know your opinion. 
 A: The real question here is "how much water"? 
But let's start with the literal question. Heating water to the boiling point (373K) just means that the lightning current heats up a resistor in the path to 373K. That means the resistor shouldn't melt at those temperatures. Is that physically possible? Sure - plenty of metals will melt at much higher temperatures. 
Back to "how much?" A lightning strike contains about 1GJ of energy, while it takes only 0.1 MJ to bring a liter of water from room temperature to boiling. That gives us an upper limit of 10000 liter if we could convert all energy, but that's of course not possible. The lightning strike will also heat up the rest of the rod, and the ground too. Still, that's plenty of water for a cup of tea.
A: Lightning can boil water. The reason why many objects explode when struck is that the water they contain vaporises. So there is enough energy available.
However, lightning is a very transient phenomenon, so the amount of water you could manage to bring to boiling point, without wasting heat on steam explosions, would be dependent on passing the heat energy into the water in a controlled way.
If you wanted to design a kettle that maximised the mass of water brought to boiling point you would need a well-insulated water jacket around an element that maximised the surface area contact between the element and the water. Bearing in mind that good conductors of electricity are typically better than water at conducting heat, you want the heat generated in the conductor to pass to the water rather than being conducted away and dissipated elsewhere. 
The element need not be a single conductor, but could instead be a bundle of spatially separated filaments offering the same resistance as a solid conductor by providing a large number of parallel paths. The filaments would be in a water bath, so that there was a very high surface area of contact with the water (which itself would conduct electricity and absorb some of the heating effect directly from the current passing through it).
Provided that each filament was surrounded by the right amount of water, you could indeed raise the water temperature to boiling point.
There would be two limits on the amount of water you could boil. The first would be the total energy of the strike. Assuming that to be a billion Joules, it would be sufficient to boil about three thousand litres.
The second would be a limit on the resistance of the conductor. If you make it too low it will not generate sufficient heat, but if you increase it too much it will fail to act as a lightning conductor.
A: The reason that lightning strikes a lightning rod rather than another point is that the lightning rod provides a path of least resistance from it to the ground. This is the reason for the 25 Ω limit in the regulations.
However, if you want to use electricity to heat something up, you need have a high enough resistance in the path of the electricity to generate heat.
Thus, you need to satisfy two opposing criteria for your lightning-rod kettle: You need to have high enough resistance in the system next to the water to heat the water, but you need to have low enough resistance so that the lightning will strike the rod and not something else. 
Is it possible to balance these two criteria to make the kettle work? I don't know. The higher the building is, the easier it will be to balance them, because the alternative paths will be longer and thus have more resistance.
