Never been to Waverly Hills myself, it's on the list but I haven't made the trip over from the UK yet. That said I've read a lot of accounts from people who've done the tours and the staircase area comes up again and again. Cold spots in general are something I find genuinely interesting because they're one of those things that's hard to explain away, especially when multiple people in the same spot report the same thing independently.
Was this during a public tour or a private investigation? And roughly whereabouts on the staircase - top, bottom, mid-landing? The detail matters I think. Would love to hear more from anyone else who's been there, particularly if you had any equipment running at the time. Even a basic thermometer reading would be useful to know about.