When he made a decree for the rain, and a way for the lightning of the thunder:
The decree regulating at what time and place, and in what quantity, the rain should fall.
A way - through the parted clouds (Job 38:25; Zechariah 10:1).
Related Commentaries of Job 28:26
Job 28:26
26 When he made a decree for the rain, and a way for the lightning of the thunder: