Most people probably do nothing. First you should measure the humidity in the room. If it never goes over 35 you probably dint need tondo anything.
Any dessicant pack will help, but if you get 70%+ humidity fir any significant length of time throughout the summer, you will want to do something to manage that.
Golden rod, dehumidifier. Im kind of pulling a number out of thin air here but it wouldnt be unreasonable to spend 10% of the value of your firearms collection on a good storage set up that protects the collection.