Lightning/Thunder NFHS Policy

[mrm21711]

I am a varsity umpire and have umpired for 6 seasons. My question is in regards to the NFHS Rule Book (Baseball) in the front with the "Guidelines on Handling Contests During Lightning Disturbances." My question is are we supposed to treat thunder (loud but no visual) the same as lightning? There has been some confusion, and I know to always err on the side of safety but am curious to the "official" correct ruling from you guys. Does the sound of thunder immediatley call for the suspension of a game, the same as lightning would? Thanks