The circuit you copied comes from India where the rain might be acid (have you seen their smog polluted air?). Acid rain conducts but the rain where you are might be pure water that does not conduct. So plug the rain detector in India.thank you ! where in the circuit should i plug the rain detector and the led ?
The sound with the series resistor is very weak because the resistor limits current from the 555 so that the 555 is not overloaded.
The 555 and the speaker can be replaced by a piezo beeper (with an oscillator in it) and could be turned on and off with a transistor.