Almost forget, the usual temperatures are from 21 degrees to 28 degrees Celcius.. Rare occasion would be 16 degrees, but usually when it occurs, all the windows would be closed.If permitted, I can post you the picture of the venue.
Just saw this thread and I don't want to discourage the idea of an acoustic grand but... it's not practical. You will need a tuner at least once a week.Keep in mind that most of your audience won't hear the piano directly but over the sound system. So what is the difference? A keyboard with sampled sounds from a top grade grand amplified or amplifying a real grand? (Placing those microphones will be a real challenge.)On some cruise ships they have shells of grand pianos where one can slide in a digital keyboard. It's the 70-80% humidity that bothers me.