Why does distilled water not conduct electricity, whereas rain water does?
The presence of ions is necessary in order for any solution to conduct electricity.
Distilled water is pure water, which is free from any kind of acids, bases or salts. Hence, it does not conduct electricity due to absence of ions.
On the other hand, before reaching the earth, rain water is mixed with several salts.These salts dissociate in water to form ions. Hence, rain water has ions in it. These ions help in conduction of electricity.