Limrock and rain

[Mudduck]

I'm taking 2 groups of 8 (@separate times) into Limrock this Saturday and noticed theres a 20% ish chance of rain. At what rain intensities does this cave become dangerous or should it be avoided with any chance of showers? I've only been to this cave one other time and it was fairly dry. My worry would obviously be getting trapped in a flooding cave. I'm planning on having each group in for a couple to 3 hours. Our backup is Tumbling Rock which I know takes a good bit of rain to have any ill effects. Thanks for any info.