How to get a cold place to purify lievito madre or how to do it without low temperatures?

Profile picture for user Juniorrpazs

I live in Brazil, Rio de Janeiro, and it's the middle of Spring.  It's humid and hoy here, and I have no idea how I'm going to create a place with a temperature between 15 and 18 degrees Celsius without spending a lot of money on a fermenter/Mini wine cellar.

How did you improvise a cold place in your house? Can the cold purification step of the lievito be replaced with something else? I intend to make panettone.