This is the 1777th most frequent Dutch word.
zodra
"As soon as."
'Zodra' is used as a subordinating conjunction to indicate that the event of raining triggers the action of staying inside.
Zodra het regent, blijven we binnen.
As soon as it starts raining, we stay inside.
Here, 'zodra' establishes a temporal relationship between his arrival and the subsequent action of offering help.
Zodra hij thuis komt, zal ik hem helpen.
As soon as he comes home, I will help him.
In this sentence, 'zodra' is used to express immediacy between the act of pressing the button and the lights turning on.