Clearly�the referee must have felt there was some danger.
I was in Nelson at the Coastal/Suburbs game, the thunder and lightening was intermittent and in the hills and no danger to anyone. Was quite exciting flying out through it. All other games proceeded. The only possible explanation was that the ground was either dangerous or unplayable. Given the state it was in after the Chatham Cup game that is quite possible but it would have been no worse than Saxton Fields.
There's plenty of spare fields around too. Game should have gone ahead.