I have also just purchased a pack of silica gel packs on amazon (saw them as I was checking on an order).
https://www.amazon.ca/gp/product/B08...ZBK0N5SNW&th=1
Last time I was in Ontario (in my Bigfoot fibreglass trailer), I had a similar issue with the fridge, though we didn't have the rain - just the normal heat & humidity. The fins iced up and stopped cooling, (freezer was fine) and I had to defrost it twice in 3 weeks.
I thought about those little dessiccant packs that come in a shoe box, or with almost anything that might be subject to moisture damage (those little "Do Not Eat" packs), and realizing that they are just silica gel in a porous packet, I made my own desiccant pack with a sock and some silica kitty litter. It helped significantly in that last week. Minimal frosting and no ice at all. Though it wasn't food grade, I made do.
That big bucket of kitty litter (had to get a gallon bucket - nothing smaller) is still in the garage, but wouldn't be any good by now.
So when I saw these little packets on amazon, I thought I would preemptively get prepared for my next trip. These 112 gm packets are good for a 2.4 cuft space - pretty much exactly the volume of my little Norcold! They are "rechargeable" by heating them to evaporate the absorbed moisture, and at $20, if it helps minimize the frost on the fins, I figured, why not? And I'll tuck one in the sock / underwear drawer while I'm at it!